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Blaptica dubia “Argentinian wood roach” Figures 111 (lateral), 112 (dorsal), 113 (ventral) Plates 67 (lateral), 68 (dorsal), 69 (ventral) The tracheal architecture of B. dubia features wide, bandlike tra- cheae and numerous visceral branches throughout the body; pre- liminary results indicate that tra- cheae may comprise nearly 12% of the volume of the insect (Herhold et al., in prep.). Spiracles and a handful of major tracheae are labeled in the figures and plates; readers are encouraged to view the 3D models provided in the supplementary digi- tal data for further investigation., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Tricholepidion gertschi “Relic Silverfish” Figures 12 (lateral), 13 (dorsal, ventral) Plates 4 (lateral), 5 (dorsal, ventral), Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Reticulitermes flavipes “Eastern subterranean termite” Figures 122 (lateral), 123 (dorsal, ventral) Plates 76 (lateral), 77 (dorsal), 78 (ventral) DESCRIPTION: HEAD: H-Oc absent, as is typical in termite workers and soldiers. H-DCT runs slightly dorsad anterior of cervix, with visceral branches dorsad and lateral. H-DCT arcing anteriad, with H-Ant branching laterally where H-DCT meets H-DVB join with H-VCT. H-VCT running directly anteriad, with split into H-MdMx branch, H-Lbm, and third branch that splits into H-DVB dorsad, H-Ft anteriad, and H-VC medially. H-Md-Mx anteriad, with H-Mx dividing ventrad. H-Md runs anteriad with short branch anteriad as second H-Ant. THORAX: T 2- S with four branches: H-DCT, H-VCT, T 2-DB, and T 2-VB. H-DCT runs mediad, curving anteriad toward head capsule. H-VCT curving similar to H-DCT, but with single T 1- L directly ventrad; T 1- AL and T 2- PL absent, but T 1-VC present, branching from T 1- L and joining medially. T 2-DB short, with T 2- AWL splitting dorsally and posteriad; T 2- DLT continues medially, splitting into Y-shaped junction with T 2- DLT posteriad and a pronounced, looping T 1- DLT joining with H-DCT. T 2- AWL arcing dorsad, bifurcating into T 2-Wbr and T 2- AL at apex of curve. T 2-Wbr runs posteriad, linking with T 3- S via T 2- PWL; T 2- AL runs ventrad, proceeding into T 2- L. T 2-VB short and running ventrad, splitting into anterior visceral branch and remaining T 2-VB, running ventrad and toward posterior as T 2- VLT. T 2-Wbr with small T 2-W-c-r and T 2-W-cu-a present. T 2-VC present, extending off T 2- VLT. T 3- S with three branches: T 2- PWL, T 3-DB, and T 3-VB. T 2- PWL anteriad from T 3- S, splitting into T 2-Wbr toward T 2- S and T 2- PL running ventrad, joining with T 2- AL and proceeding into midleg as T 2- L. T 3-DB runs directly mediad, with T 3- AWL branch arcing posteriorly close to T 3- S; remining T 3-DB runs further mediad, joining with T 2- DLT from anterior and proceeding as T 3- DLT toward posterior. T 3- AWL arcing posteriorly, splitting into dorsal T 3-Wbr and ventrad T 3- AL. T 3-W-c-r and T 3-W-cu-a not visible off T 3-Wbr but likely present and very small. T 3-VB runs ventrad with anterior branch leading to T 2-VL. T 2-VB continuing ventrad, joining with T 2- DLT anterior and T 3- DLT posterior in Y-shaped junction. T 3-VC present, branching medially off T 3- DLT. ABDOMEN: A 1..8- S present. Short A n -SB possible on several segments. Nearly all A n -DB and A n -VB with visceral branches that occasionally span several segments. A 1- S with three branches: T 3- PWL, A 1-DB, and A 1-VB. T 3- PWL joining medially from anterior, completing link between T 3- S via T 3-Wbr. A 1-DB runs mediad and slightly ventrad, with A 1-DB- Vi branching ventrally while A 1-DB, smaller, continuing medially to join T 3- DLT from anterior and A 1- DLT to posterior in Y-shaped join. A 1-VB runs ventrad, splitting off A 1-VB-Vi with A 1-VB continuing ventrad with T 3-VL lateral before A 1-VB splits to join T 3- VLT from anterior and A 1- VLT to posterior; A 1-VC present, branching off A 1-VB. Remaining A 2..8- S with just A n -DB and A n -VB branches. A n -DB runs mediad and slightly ventral, meeting A n - DLT branches from anterior and posterior in Y-shaped junction. A n - DLT typically small and sinuous. Large A n -DB-Vi typical for all segments, often asymmetric and extending into various abdominal regions and occasionally spanning several segments. A n -DC absent. A n -VB runs ventrad, following body wall, continuing to form A n -VC. Large A n -VB-Vi also typical for all segments; directional notation in 3D supplemental models for visceral tracheae is to denote relative directions for clarity and not an assessment of homology. A n -VB with small A n -MLT branching ventrad from A n - S, directly posteriad toward proceeding posterior segment, linking with A n -VB. As with A n - DLT, A n -MLT often small and hard to distinguish, occasionally not visible on one side of the specimen but likely present., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Romalea microptera “Eastern lubber grasshopper” Figures 63 (lateral), 64 (dorsal, ventral) Plates 38 (lateral), 39 (dorsal), 40 (ventral) The tracheal structure of the lubber grasshopper Romalea microptera features a substantial number of air sacs, integrated into the tracheal system, and discrete air cells distributed throughout the body, especially the head and thorax. Due to the complexity of the tracheal architecture of Romalea, only spiracles and major tracheae are labeled in the plates. 3D models are provided in the supplementary digital data for further investigation., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

ORDER ZYGENTOMA There are very few micro-CT studies of Zygentoma to date; most notably, synchrotron radiation micro-CT of Tricholepidion gertschi heads has been used to investigate Zygentoma morphology for systematic study (Blanke et al., 2014), but not tracheae. This genus is particularly significant given the disputed placements within and near Zygentoma (Engel, 2006; Blanke et al., 2014). Zygentoma are relevant in general as a sister group to the pterygotes, and indeed they share several tracheal synapomorphies. Three specimens from two orders were scanned here: Thermobia domestica and Lepisma saccharinum from Lepismatidae, and the relict silverfish Tricholepidion gertschi from Lepidotrichidae. Scan resolutions were within a 2.4 µm 3 /voxel range, with Lepisma at the highest resolution of 4.8 µm 3 /voxel and Thermobia with the lowest resolution at 7.2 µm 3 /voxel. Resolving the smallest tracheae at these resolutions tends to be more a function of specimen preservation rather than scanning parameters. Although the level of detail varies slightly between these scans, sufficient resolution was achieved to locate small visceral tracheae in all three specimens, indicating suitability for comparative purposes. Although the zygentoman head morphology is similar among the specimens, in the sections below Lepidotrichidae thoracic and abdominal detail are described separately due to substantial differences. Tricholepidion appears to possess only two pairs of functional abdominal spiracles, A7-S and A8-S. The elongate, sinusoidal trunks beginning at A7-S and extending anteriorly to the thorax are not present in the two lepismatid specimens. If Tricholepidion is indeed basal to Lepismatidae, it is possible that these trunks are plesiomorphic, and a loss of these tracheae in Thermobia and Lepisma could be derived. In both species scanned from Lepismatidae, leg tracheae branch from T2-S and T3-S in an arc leading posteriorly into the legs, each with a small branch extending dorsad. Here we interpret these as T2-AWL and T3-AWL, with T2-AWba and T3-AWba branching dorsad. An alternative pattern is to designate these dorsal branches as simply T2,3-L-DVi, but the similarity of the branching pattern with both apterous and winged taxa included herein (e.g., Grylloblatta) strongly suggests homology with these wing base tracheae; Šulc (1927) interpreted these as possible wing tracheae. DESCRIPTION: HEAD: H-DCT with two branches: H-Ft dorsal; H-Ant-Lbr anteriad and slightly ventral, dividing into H-Ant and H-Lbr close to base of antenna. H-VCT with three branches, dividing at approximately same location: small H-Lbm extends ventrally; H-Mx continues anteriorly before proceeding ventrad; larger H-OcMd extends anteriorly. H-VC absent in T. gertschi but present in both Lepismatidae. H-Oc branching dorsally, H-Md continues anteriorly and ventrad, following shape of mandibular sclerite. THORAX: Tricholepidion with significant differences among Zygentoma, notably T2-DLT and T3-DLT elongate, with dorsal visceral branches similar to T2-DB and T3-DB; a complete description of the thorax of Tricholepidion thorax is below. For both Lepismatidae: T2-S with three branches: T2-CT, T2-AWL, and T2-VB. T2-CT very thick, running directly anteriad with T2-DB just anterior to T2-S; T2-CT dividing into H-DCT and H-VCT in prothorax. Thinner T2-AWL arcing posteriorly, slightly dorsad, with thin but prominent dorsad and posteriorly arcing T2-AWba. T2-ACx present with T2-VC, remainder of T2-AWL extending into midleg as T2-L. T2-DB dividing into T2-DLT, extending in posterior arc and T1-DLT, ending blind in prothorax. Small T1-Pn present just anterior of H-DCT/H-VCT split. T1-L branching ventrally from H-VCT; T1-L with T1-VC branch present; T1-ACx from T1-VC; T1-PCx from T1-L. Small T2-VB with T2-VB-Vi. T2-L two branches: prominent, dorsad and posteriorly arcing T2-L-DVi. Thermobia with T2-PCx from T2-L, note that T2-PCx is from T2-VB in Lepisma. T2-VC with connection from T3-AsymC medially, originating from left side in Thermobia and right side in L. saccharinum. T3-S with three branches: T3-DB, T3-AWL, and T3-VB. T3-DB directly dorsal with Y-shaped bifurcation to T2-DLT from anterior and T3-DLT toward A1-S. T3-AWL posteriad with T3-AWba, longer in Lepisma than Thermobia. T3-PCx from T3-L in T. domestica, T3-VC in L. saccharinum. T3-VB ventral and slightly inward with AsymC from left side of T. domestica, right side of L. saccharinum, anteriad to connect with T2-VC. ABDOMEN: T. gertschi with significant differences to other Zygentoma, including apparent lack of functional abdominal spiracles (except A7-S and A8-S), and a sinusoidal A7-VLT extending anteriorly over several segments; a complete description of abdomen is below. For Lepismatidae: A1..8-S present, all located laterally. A n -SB present for segments in middle of abdomen but variable; see detailed descriptions. A n -S (or A n -SB) with A n -DB and A n -VB present. A n -DB running dorsad, bifurcating into Y-shaped junction with A n -DLT anteriad and posteriad; all abdominal segments connected via dorsal trunk. A n -VB running ventrad, connecting with opposite side via thin A n -VC; A1..7-VC present in T. domestica, A4..7-VC not visible in L. saccharinum scan but likely present; A8-VC absent. A n -DB-Vi and A n -VB-Vi numerous, see sections below for details. A8-DB and A8-VB large, curving medially before proceeding posteriad; A8-DB with A-TF and A-Cr in T. domestica but not visible in L. saccharinum scan (presence/ absence ambiguous)., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Blanke, A., M. Koch, B. Wipfler, F. Wilde, and B. Misof. 2014. Head morphology of Tricholepidion gertschi indicates monophyletic Zygentoma. Frontiers in Zoology 11 (1): 16 - 16.","Engel, M. S. 2006. A note on the relic silverfish Tricholepidion gertschi (Zygentoma). Transactions of the Kansas Academy of Science 109 (3 / 4): 236 - 238.","Sulc, K. 1927. Vzdusnicova soustava lepismy (Thysanura) a puvid kridlateho hmyzu. Acta Societatis Scientiarum Naturalium Moravicae 4 (7): 1 - 108."]}

“American cockroach” Figures 107 (lateral), 108 (dorsal), 109 (ventral) Plates 64 (lateral), 65 (dorsal), 66 (ventral) The P. americana specimen here was scanned early in the study, frozen to -20° C rather than -80° C, and at relatively coarse resolution (38.6 µm, specimen approximately 3.5 cm in length). Some fluid infilling likely occurred due to the freezing to -20° C, but sufficient detail is present to assess homology of major tracheae and discern substantial visceral tracheal anatomy. Although not described in detail, Blaptica was used as a comparison to infer the likely presence of thoracic tracheae in Periplaneta , in particular branching patterns from the mesothoracic spiracle. The thorax features a network of bandlike visceral tracheae along the dorsum and venter, connecting in various locations throughout. This morphology, combined with the long, broad coxae reminiscent of silverfish, obscures internal thoracic tracheal structures in two-dimensional views. The hypognathous position of the head also results in ventral tracheal views of the thorax being obscured; see figure 110 for a ventral view with head and leg tracheae removed. Periplaneta has large air spaces in the coxae, and jumping has been filmed at high speed by Smith (2022). The scan here is of relatively coarse resolution (38 µm); it is possible muscle tracheae could be observed at higher resolutions or with contrast-enhancing stains such as iodine or phosphotungstic acid (Gignac et al., 2016). DESCRIPTION: HEAD: H-DCT and H-VCT present, branching into head capsule in highly networked cagelike arrangement. Mouthparts, H-Ant, and H-Oc determined, but networked nature of head morphology, combined with some apparent fluid infilling, makes assessing homology difficult. Readers are directed to 3D models in the supplementary digital data. THORAX: T2-S with five branches: H-DCT, H-VCT, T2-DB, T2-AWL, and T2-VB. H-DCT and H-VCT both anteriad, curving slightly medially, with H-DCT proceeding along dorsum and H-VCT along venter. T1-AL branching ventrad off H-VCT. T2-DB short, splitting anteriad into T2-DLT and posteriad as network of cagelike T1-DVi along pronotum. T2-AWL posteriad, with T2-W-c-r splitting dorsad and posteriorly; T2-AWL splits into T2-AL extending into midleg and T2-Wbr, partial in this scan but likely present between T2-S and T3-S. T2-VB likewise short, bifurcating into T2-VC directly ventrad and T2-VLT posteriad. T2-VL branching posteriad close to T2-S, extending into midcoxa and T2-L; T2-VLT continuing posteriad to link with T3-S. T3-S with n branches: T2-PWL, T3-DB, T3-AWL, T2-VLT, and T3-VLT. T3-VB not visible but may be very short. T2-PWL anteriad from T2-S, bifurcating into T2-Wbr anteriad and curving posteriad as T2-PL, joining with T2-AL from anteriad and extending into mid-leg. T3-DB mediad and slightly ventrad, curving posteriorly before extending along dorsum to join with small T2-DLT anteriad and larger T3-DLT posteriad; T3-DC visible at this junction. T3-AWL posteriad, with T3-W-c-r splitting dorsally; T3-AWL continues as T3-AL posteriorly and ventrad into hind leg. T2-VLT mediad, connect- ing anteriorly to T2-S. T3-VLT mediad and slightly posterior, connecting to A1-S via A1-VB. ABDOMEN: Abdomen featuring numerous visceral tracheae throughout. A1..8-S present. A1-S modified from A2..8-S, with three branches: T3-PWL, A1-DB, A1-VB. T3-PWL anteriad and slightly mediad, curving posteriorly and joining with T3-AL and extending into hind leg; T3-Wbr branching from T3-PWL at apex of curve and extending anteriad to T3-S. A1-DB runs mediad, linking with T3-DLT anteriad and A1-DLT posteriad; A1-DB partial in this scan, likely due to fluid infilling (A1-DB present in B. dubia and G. portentosa). A1-VB mediad and slightly ventrad, extending along venter to A1-VC, connecting to A1-VLT posteriad; A1-MLT posteriad from A1-VB. A n -MLT runs straight, extending posteriad and much smaller than thoracic T3-VLT. A2..7-S branching all similar: A n -DB, A n -VB, and A n -MLT. A n -DB beginning small, expanding into bandlike trachea and intersecting with A n -DLT sections anteriorly and posteriorly in Y-shaped junctions; A n -DC absent. A n -MLT wide and almost bulblike, connecting abdominal spiracles along lateral margin of body wall. A n -VB much smaller and apparently fluid infilled in several spiracles, extending along venter to join with straight A n -VLT anteriad and posteriad in T-shaped junction. A4..8-S with numerous visceral tracheae; readers are encouraged to view 3D models in supplementary digital data., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

ORDER PLECOPTERA Respiration in stonefly naiads via gills has been studied for decades, partly because of the significance of stoneflies as indicators of water quality. Two plecopteran specimens were scanned, one from Perlodidae and one from Nemouridae. The Nemouridae scan, at 3 µm resolution, shows substantially more smaller tracheae than the Perlodidae, scanned at 6 µm. Cromulent detail is present in both specimens to assess homology. Numerous visceral tracheae branch from A4-DLT-Dvi and extend throughout the abdomen. Tracheae from A4-DLT-Dvi are pervasive throughout the abdomen, leading to the question of why this particular spiracle is so important. Other insects have adapations for individual spiracles, such as the single abdominal “hissing” spiracle in Gromphadorhina (Nelson, 1979; Nelson and Fraser, 1980; Heinrich et al., 2013), but the presence of tracheae throughout the abdomen indicates a likely respiratory function. Future studies should investigate O 2 input versus CO 2 output, for example. The perlodid specimen scanned here is another example of cooption of the gut as an air space in nonfeeding adults. Likely for weight reduction, this condition also seen in mayflies and male Embioptera. Other notable open issues include ventral visceral VVi tracheae in Perlodidae that are likely VC, as these are present in Nemouridae. Additionally, T2,3-VLT are present in Nemouridae but not Perlodidae. It is possible that the absence of T2,3-VLT in Perlodidae is a preservational artifact and scanning of further specimens is indicated to verify these features. DESCRIPTION: HEAD: The two specimens differ in life history: adult Nemouridae, in the Group Euholognatha, have functional mouthparts adapted for feeding on algae, lichens, or soft pollen; while Perlodidae, in Systellognatha, is known to have adults with reduced mouth parts that typically do not feed. Consequently, head morphology is different enough to describe each family in the sections below. THORAX: Thoracic tracheal morphology is largely similar between the two species scanned but with substantive differences; thoraces for both are described here for comparative clarity and also detailed in family sections below. Large thoracic air spaces present in both species, but spherical nature of air spaces in Nemouridae indicates possibility of preservational artifact (see fig. 50). Putative air sac in Perlodidae begins in thorax, extending into abdomen. T2-S with four tracheae: T2-CT, T2-DB, T2-VB, T2-AWL. T2-CT very thick, proceeding anteriorly in sinusoidal curve; Nemouridae with two branches off T2-CT: T1-L extending ventrad, and T1-Gi just posteriad of cervix. T1-Vi present. T1-L with tibial trachea greatly enlarged relative to femoral trachea. T2-DB running directly mediad, arcing posteriorly to continue as T2-DLT, with a number of T2-DLT-Dvi branching dorsally, likely into flight muscle; Nemouridae with large T2-FM extending dorsad close to T2-S; T2-Fm arcs medially to connect to opposing side as T2-DC; T2-FM off T2-DLT and T2-DC not visible in Perlodidae. T2-VB posteriad and ventrad; in Perlodidae, blind ending near mesocoxae; T2-VC present, positioned approximately halfway between procoxae and mesocoxae. T2-VB asymmetric in Nemouridae; on right side, extending ventrad and posteriad, arcing dorsally just anterior to mesocoxae to link with T3-S via T2-DLT, while on left side, T2-VB mirrors right side but turns abruptly mediad to link with T2-VB on left side, forming T2-VC. T2-VB in Nemouridae with multiple T2-VB-Vi that likely supply flight muscle; single large T2-VB-Vi extending directly from T2-S on left side but mirroring similar T2-VB-Vi from T2-VB on right side. T2-VB-Vi not visible in Perlodidae scan. T2-AWL begins dorsally, turning posteriorly and ventrad toward midleg, joining T2-PL ventrally from T3-S; T2-AWL with a sharp turn posteriad in Perlodidae, likely where T2-AL and T2-Awba (or T2-Wc-r) would split but not visible in this scan; in Nemouridae T2-AWL short, with T2-AL and T2-W-c-r bifurcating just dorsal to T2-S. T2-AL tracheal lumen not visible and likely fluid filled in right side of Perlodidae; left side of same specimen with short gap and smaller trachea connecting. T2-AL complete in Nemouridae. T2-W-c-r extending dorsally and posteriad into wing. T2-W-c-r not visible in Perlodidae. T3-S with four connections: T3-DB, T3-VB, T2-PWL, T3-AWL. T3-DB short and directed inward, linking with T2-DLT anteriorly and T3-DLT posteriorly; large T3-FM runs dorsad where T3-DB joins T2-DLT and T3-DLT. T3-FM running dorsad with several tracheae extending into flight muscles; T3-FM continues dorsad, arcing medially to join with opposite side via T3-DC; T3-DC not visible in Perlodidae but likely present. T3-VB runs ventrad and posteriad, with numerous branches extending into flight muscle; T3-VB with T3-VC branch inward, meeting opposite side, near ventral sternite. In Nemouridae, T3-VB on left side continues as T3-VLT, linking with A1-S; T3-VLT absent on right side. T3-VLT not visible in Perlodidae. T2-PWL running directly anteriad, bifurcating into T2-Pwba extending dorsally and anteriad and T2-PL, mediad. T2-PWBa continues dorsally, with several branches into flight muscle and single, small T2-W-cu-a extending into trailing edge of forewing. T2-PL arcing medially and ventral before turning laterally, joining with T2-AL from anterior and extending posteriorly into T2-L. T2-L with tibial trachea greatly enlarged relative to femoral trachea. T3-AWL running ventrad, just medial from T3-S, with small T3-W-c-r branching dorsally where remaining trachea turns posteriad into T3-AL. T3-W-c-r not visible in Perlodidae but likely present. ABDOMEN: Abdominal morphology largely similar between Perlodidae and Nemouridae, with overall structure described here and specific differences given below. Air sac in Perlodidae extends as far as A3-S (fig. 50). A[1..8]-S present. A1-S branching modified from remaining abdominal segments, with slight differences between Perlodidae and Nemouridae. Both specimens with A1-DB and A1-VB; Perlodidae with T3-Pwba directly from A1-S, Nemouridae with T3-Pwba from A1-VB slightly ventrad from A1-S. Both T3-Pwba anteriad and slightly dorsad, splitting into several smaller visceral tracheae likely supplying flight muscle and single T3-W-cu-a into trailing edge of hind wing. A[1..8]-DB and A[1..8]-DLT present in both taxa, with numerous visceral tracheae from DLT detailed in sections below. A[1..8]-VB, A[2..8]-SB, A[1..8]-VC present in Nemouridae but absent (or not visible) in Perlodidae. See family-level sections for descriptions of visceral tracheae.

Zootermopsis angusticollis Soldier caste “Dampwood termite” Figures 118 (lateral), 119 (dorsal), 120 (ventral) Plates 73 (lateral), 74 (dorsal), 75 (ventral) DESCRIPTION: HEAD: Major tracheae indicated in plates, due to networked nature of head tracheae, readers are referred to 3D models in supplemental digital data (see “Availability of Digital Data,” above). H-Oc notably absent, as is expected in termite soldiers. H-DCT with Y-shaped branch meeting in midline as H-DCMedB, which loops posteriad to rejoin H-DCT near origin of Y-shaped branch. Two branches at anterior end of H-DCMedB-Loop: H-Ant anteriad and H-DVB directly ventrad, linking with H-VCT on each side. Close to origin of Y-split, H-DV-Loop extends laterally and anteriad in wide arc, following head capsule lateral wall, looping medially and posteriad near base of antenna, connecting with anterior end of H-VCT as H-DV-Loop; additional H-Ant extends from anterior end of H-DV-Loop. H-VCT runs directly anteriad along floor of head capsule, with large H-DVB connecting to H-DCT and H-DCMedB-Loop. Remainder of H-VCT anteriad toward mouthparts, linking with H-DV-Loop, and branches extending to H-Md, H-MxPlp, and H-Lbm along this loop. H-VLT present, extending into labium. H-VLT asymmetric in soldier caste, see figure 121 for ventral view of worker caste showing symmetric H-VLT branches. THORAX: T 2- S with four branches: H-DCT, H-VCT, T 2-DB, and T 2-VB. H-DCT mediad, curving anteriad toward large head capsule; short T 1- DLT from T 2-DB connecting before curve. H-VCT like H-DCT, with ventrad T 1- AL near curve toward anterior. T 2-DB short, with T 2- AWL branch running posteriad close to T 2- S; T 2-DB continues mediad with Y-shaped bifurcation of short T 1- DLT anteriad toward H-DCT and T 2- DLT posteriad toward T 3- S. T 2- AWL arcing posteriad, splitting in to T 2- AL and T 2-Wbr at apex of arc; T 2-Wbr with small T 2-W-c-r and T 2-W-cu-a, connecting with T 2- PWL posteriorly; T 2- AL posteriad and ventral, joining T 2- PL and extending into midleg. T 2-VB runs directly mediad, bifurcating into T 2-VC1 mediad and T 2- VLT arcing ventrally and posteriad along sternite. T 2-VC1, the first of two mesothoracic ventral commissures, proceeding mediad with T 1- PL branch directly ventrad and smaller connection anteriad to T 1-VX. T 1-VX with H-VCT extending anteriad into head; single branch on specimen left side but likely present on right—see T 2-VC2 branching mediad from T 2- VLT anteriad from T 2-VLT’s curve dorsad toward T 3- S; T 2- VLT with additional T 2-Cx branch, larger on right side than on left. T 3- S with four branches: T 2- PWL, T 3-DB, T 3- AWL, and T 3-VB. T 2- PWL from anterior, connecting T 2- PL and T 2-Wbr from T 2- S. T 3-DB mediad, joining with T 2- DLT and T 3- DLT in flat Y-shaped junction. T 3- AWL mediad briefly, arcing posteriad and dorsally, splitting into T 3- AL ventrad into hindleg and T 3-Wbr posteriad, joining with A 1- S via T 3- PWL. T 3-Wbr with small T 3-W-c-r anterior and T 3-W-cu-a posterior. T 3-VB runs directly ventrad, with T 3- VLT splitting posteriorly just ventrad of T 3- S. T 3-VB continuing ventrad, with T 2-VL branch ventrad and posteriad, extending into midleg; remaining T 3-VB arcing medially to form T 3-VC1; T 2- VLT joining with T 3-VB near this arc. T 3- VLT ventrad, arcing posterior along sternite before continuing anteriad toward A 1- S, with T 3-VC2 mediad near apex of this arc. T 2- VLT and T 3- VLT both with two ventral commissures: posterior T 2-VC2 and anterior T 3-VC1 along same section of T 2- VLT; posterior T 3-VC2 and A 1-VC both along same section of T 3- VLT. ABDOMEN: A 1..8- S present. Short A n -SB possible on several segments. A 1- S with three branches: T 3- PWL, A 1-DB, and A 1-VB; remaining A 2..8- S with just A n -DB and A n -VB branches. For A 1- S, T 3- PWL from anterior, completing T 3-Wbr link from T 3- S. A n -DB runs mediad and slightly dorsad, meeting A n - DLT branches from anterior and posterior in Y-shaped junction. Large A n -DB-Vi typical for all segments, often asymmetric and extending into various abdominal regions and occasionally spanning several segments. A n -DC absent. A n -VB runs ventrad, following body wall, continuing to form A n -VC; A 8-VB split into A 8-VC1 anterior and A 8-VC2 posterior. A n -VB with A n -MLT branching ventrad from A n - S, directly posteriad toward proceeding posterior segment, linking with A n -VB. A 5..8-MLT slightly modified, connecting nearly directly with subsequent A n - S. As with A n -DB, A n -VB-Vi extend throughout abdomen; A 7-VB-Vi and A 8-VB-Vi extend mediad, crossing middle of body and extending anteriad past A 4- S., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Gromphadorhina portentosa “Madagascar hissing cockroach” Figures 114 (lateral), 115 (dorsal), 116 (ventral) Plates 70 (lateral), 71 (dorsal), 72 (ventral) Easily the most popular cock- roach (as far as cockroach popular- ity goes), the physiology of the hissing behavior of G. portentosa was investigated by Nelson and col- leagues (Nelson, 1979; Nelson and Fraser, 1980), with the notable find- ing that the fourth spiracle (A2-S) is the source of the hiss. Heinrich et al. (2013) documented unidirectional airflow in G. portentosa resulting from spiracular valve control. As seen in the plates, the tracheal archi- tecture of Gromphadorhina is remarkably complex, so only spiracles and major tracheae are labeled here. As is common in reared Gromphadorhina colonies, the individual scanned was infested with mites (see fig. 117), likely Gromphadorholaelaps schaeferi, found to be possibly beneficial by Yoder et al. (2012)., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Yoder, J. A., J. B. Benoit, B. Z. Hedges, A. J. Jajack, and L. W. Zettler. 2012. Madagascar hissing cockroach mite, Gromphadorholaelaps schaeferi, prevents fungal infection in its cockroach host: evidence for a mutualistic symbiosis. International Journal of Acarology 38 (5): 427 - 435."]}

ORDER PHASMATODEA Tracheal architecture of stick insects has most recently been investigated by Strauss (2021), with an emphasis on the prothorax and possible adaptations for sound reception. Here, three specimens were scanned: the basal Timema cf. californicum, the popular Australian stick insect Extatsoma tiaratum, and the Vietnamese stick insect Medauroidea extra- dentata. Although many basal taxa exhibit synapo- morphies found in sister taxa of a given monophyletic group, Timema exhibits numerous apomorphies and its tracheal system is quite distinct from Extatosoma and Medauroidea. Medauroidea appears to be more representative of the larger phas- mids, with good scan quality and characters that appear to be common to Extatosoma (which is more complex and somewhat harder to homolo- gize). Timema and Medauroidea are described here in detail; Extatosoma is covered here in a more basic fashion due to the substantial complexity in the abdomen. Future studies should focus on the unique morphology of the abdominal tracheae—resem- bling the jumble of dried, packaged ramen noo- dles—of Extatosoma and its possible functions.

Neocloeon triangulifer subimago “Triangle small minnow mayfly” Figures 24 (lateral), 25 (dorsal, ventral) Plates 14 (lateral), 15 (dorsal, ventral) DESCRIPTION: BODY: Several alimentary canal air spaces present, fusing into single one in adult. HEAD: H-DCT and H-VCT similar in size, extend into head capsule from prothorax. THORAX: T 1-DVi branches from H-VCT on left side, H-DCT on right. ABDOMEN: A 2..7-Gi gill attachments visible laterally on A n - DLT, midway between spiracles; A 1-Gi on posteroventral extension from A 1- S, reduced in adult (no other vestiges of gill attachment sites present in adults). Several dorsal visceral tracheae extend anteriorly beyond segment boundaries; ventral Vi (retained) within segment., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Meconema thalassinum “Drumming katydid” Figures 67 (lateral), 68 (dorsal, ventral) Plates 43 (lateral), 44 (dorsal, ventral) The female drumming katydid we scanned is likely a late-stage instar due to the reduced wings. T 2-DB-Vi and T 3-DB-Vi each form a trapezoidal set of double dorsal commissures. It is possible that these may be homologous with sausagelike dorsal commissures seen in other taxa that might be for weight relief or could be involved in stridulatory sound dissemination. DESCRIPTION: HEAD: Three pairs of tracheae into head: H-DCT, H-VCT, and H-VLT. Head with several interconnected dorsoventral and lateral loops; readers are encouraged to review the supplementary 3D digital models. Air space, possibly a preservational artifact, present in right side of head capsule (see fig. 69). H-DCT runs anteriad, curving dorsally along head capsule and curving medially to connect in a loop just dorsal of eyes. H-DC present. Anteriad of cervix, H-DCT-Oc branches ventrad, linking with H-VCT-Oc with Y-shaped junction to H-Oc-Md. Several small, visceralike H-Oc run dorsad from H-Oc-Md; H-Oc-Md anteriad, reconnecting to H-VCT with H-Md branching anteriad, with lateral H-FtC branch linking left and right side. H-VCT runs anteriad with ventral curve; T 1- AL running posteriad prior to H-VCT entry to head capsule. H-VCT with aforementioned H-VCT-Oc branch running anteriad; H-VCT continuing anteriad with ventral branch, linking with H-VLT before continuing into H-Mx and H-Lbm split. THORAX: T 2- S opening very large, positioned under pronotum; T 2- S with five branches: T 2-DB, T 2-VB, H-DCT, H-VCT, and T 1- PL. Several tracheae behind T 1-DVi; see figure 70 for view rotated to see additional detail. Readers are also directed to 3D models from supplemental digital data. T 2-DB and T 2-VB from short dorsal spiracular branch, extending directly dorsad and ventrad, respectively. T 2-DB with T 2- AWL split, with T 2-DB continuing dorsad, connecting with T 2- DLT extending posteriorly. T 2- AWL runs dorsad with sharp curve directly ventrad toward midleg; T 2-W-c-r positioned posteriad at apex of curve. T 2-VB runs directly ventrad from T 2-DB/ T 2-VB split, arcing posteriad to connect with T 2- VLT; several small visceral branches forming cagelike network along venter. H-DCT runs dorsad from T 2- S, arcing anteriad and continuing through prothorax into head capsule; T 1-DVi branches forming cagelike morphology along inner wall of protergum, around H-DCT. H-VCT runs dorsad, arcing ventrad before turning anteriad into head capsule, arranged along outside of enlarged T 1- PL; T 1- AL with ventral branch anteriad of T 1- PL. T 1- PL greatly enlarged in hornlike arc, reducing in size and extending into proleg. T 1-L-Ty tympanum present on foreleg tibia. T 3- S much smaller than T 2- S, with five branches: T 3-DB, T 2- PWL, T 3- AWL, T 3-VB, and T 2- PL. T 3-DB and T 3-VB split dorsad and ventrad after short dorsal spiracular branch from T 3- S. T 3-DB running directly dorsad, with T 3- AWL branching dorsad and slightly lateral; T 3-DB continuing dorsad to join with T 2- DLT from anterior and smaller T 3- DLT posteriad. T 3- AWL runs dorsad, with sharp curve ventrad and posteriad toward midleg. T 3- AWL with two connections to tracheae leading to A 1- S: T 3-Wbr, branching dorsally at apex of curve, with T 3-W-c-r and T 3-W-cu-a dorsad; and apparent T 3- PWL extension, dorsal and anteriad from A 1- S, connecting with T 3- AWL / T 3- AL. (See Discussion on Orthoptera.) T 3-VB runs mediad and ventrad, connecting with T 3- VLT toward posterior and T 2- VLT anteriad. T 2- PL ventrad with curving T 2-pf branch to T 2- VLT; T 2- PL continues into midleg, joining with T 2- AL. ABDOMEN: A 1..8- S present. A 1- S modified, positioned slightly dorsad relative to A 2..8- S. A 1- S with four connections: A 1-DB, T 3- PWL, A 1-VB, and T 3- PL. Single A 1-DB runs dorsad and slightly anterior, broad and flat; intersecting with T 3- DLT anteriad and A 1- DLT posteriad. Several small visceral-type tracheae connecting with T 3- PWL and and likely extending into flight musculature. T 3- PWL running dorsad and anteriad, similar to A 1-DB but smaller; T 3- PWL splitting slightly dorsad into T 3-Wbr anteriad connection to T 3- S, and smaller unnamed extension connecting to T 3- AL (see THORAX, above, and Discussion section on Orthoptera). T 3- PL thick, running directly ventrad from A 1- S, connecting with smaller T 3- AL from metathorax and extending into hind leg. T 3-VL present, extending into hind leg from T 3- VLT. A 1-VB runs ventrad and slightly mediad, connecting with T 3- VLT from anterior and A 1- VLT posteriad. A 2..8- S similar, each with anterior and posterior dorsal branches A n -ADB and A n -PDB, both intersecting with A n - DLT along dorsum. A n -VB short, running ventrad and slightly mediad, connecting directly to A n - VLT along venter. X-shaped commissures positioned ventrad to VLT (see fig. 71). Numerous visceral tracheae present in abdomen, often spanning several segments, but none appearing to connect segments longitudinally., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Aeshna sp. immature Figure 30 (lateral, dorsal, ventral) Determining the correct placement and assessment of homology of the longitudinal trunks in the aeshnid adult required the scanning of an aquatic immature. The closed tracheal system of the naiad dragonfly is built around the rectal gills, and was first detailed by Scott (1905) and Tillyard (1917), whose terminology we adapt here. The aeshnid naiad possesses four paired longitudinal trunks in the abdomen, one more than determined by Tillyard (1917). His Dorsal Trunk DT is our A n -DLT, and we adapt his Visceral Trunk VT as Visceral Longitudinal Trunk A n -VLT. However, Tillyard’s Ventral Trunk VNT is actually homologous to the Medial Longitudinal Trunk A n -MLT, as it follows the spiracles along the lateral body wall (see description for adult, below). The abdominal A n -VLT is depicted as shorter ventral branches (but not labeled) by Tillyard in his fig. 75 (fig. 28). In figure 30 here it is barely visible in the ventral view but likely present as a longitudinal trunk. This specimen was collected early in the study and frozen to -20° C rather than -80° C, possibly causing smaller structures to be infilled with fluid, and the 30 µm scan resolution is not ideal for capturing smaller details such as these fine tracheae. Regardless, the presence of the branches leading to these more linear, ventrally located tracheae indicates that these are indeed A n -VLT., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Scott, G. G. 1905. The distribution of tracheae in the nymph of Plathemis lydia. Biological Bulletin 9 (6): 341 - 354.","Tillyard, R. J. 1917. The biology of dragonflies (Odonata or Paraneuroptera). London: Cambridge University Press."]}

Oligotoma negra “Black webspinner” Figures 75 (lateral), 76 (dorsal, ventral) Plates 47 (lateral), 48 (dorsal, ventral) The respiratory system of Embioptera remains rather understudied, with the most recent detailed analysis of tracheal anatomy by Lacombe (1958, 1971). The specimen of Oligotoma shown here is a male and is notable because of the air-filled alimentary canal (fig. 77). Male webspinners do not feed, and like Ephemeroptera (fig. 21), the alimentary canal is coopted as a large air space, spanning the length of the body. In this specimen, the distention of the alimentary canal compressed tracheae against the inner body wall, making determination of morphology and assessment of homology challenging (particularly in the abdomen). Some notable differences were observed between Lacombe (1958) and the specimen here, particularly in the thorax, but her work was useful in mapping abdominal tracheae. The meso- and metathoracic wing base T 2,3- Wbr are likely present but partial in this scan, likely due to fluid infilling of this specimen as it was frozen to -20° C rather than -80° C. Although a tympanal hearing organ in the femur (of pro- and mesoleg, and occasionally hind leg) of webspinners was described by Szumik et al. (2019), there is no evidence of an air space in femur of any leg (as seen here in the foretibia of Gryllus, for example). DESCRIPTION: HEAD: H-DCT extending anteriad, curving laterally along head capsule; H-VCT slightly ventrad. H-DC present, slightly anterior of cervix. H-DCT with H-DCT-DVi running dorsad anterior of cervix, following head capsule. H-DCT runs directly anteriad, dividing into H-DVB ventrad and H-Ant. H-VCT with H-VCT-DVi extending dorsally, nearly in contact with H-DCTDVi and following head capsule laterally. H-VCT continues anteriorly, with dorsal H-DVB connection to H-DCT. After short extension, H-VCT divides into H-Lbm, and subsequently into H-MxPlp, H-Md, and H-Oc. H-Lbm branch connecting mediad as H-VC. Branch leading to H-Oc continues to H-Ft. THORAX: T 2- S with four branches: H-DCT, H-VCT, T 2-DB, and T 2-VB. T 2- CT absent. H-DCT runs directly anteriad, with T 1-DVi branching dorsad before continuing dorsally along prothoracic tergum. T 1-DC present, extending mediad near branching of T 1-DVi. H-VCT runs anteriad, with T 1- L branching ventrad just prior to a nearly 90° turn ventrad, subsequently turning anteriad along prothoracic sternite. T 1-VC present, branching off T 1- L. T 2-VB runs posteriad and slightly ventral briefly before curving dorsad; small T 2- AWL branching anteriad at apex of curve, dividing into T 2-AWba dorsad and T 2- AL continuing posteriorly toward midleg. T 2-DB continues, curving medially with several branches, likely for flight muscle, before extending posteriad as T 2-ADLT. Full DLT not visible but likely present, possibly fluid infilled; Lacombe (1958) indicates presence of dorsal connective. T 2-VB runs posteroventrad, with large T 2- FM branching dorsad and laterally. T 2-VB continues as T 2- VLT, connecting with T 3- S. T 2-VC present, branching mediad approximately halfway between T 2- S and T 3- S. T 3- S with four branches: T 3- AWL, T 2- PWL, T 3-DB, and T 3-VB. T 3- AWL running dorsad, curving posteroventrad where T 3-W-c-r splits dorsally and remaining branch continues as T 3- L. T 2- PWL connecting directly from anterior; T 2- PL branching ventrally, joining with T 2- AL after a short distance and continuing as T 2- L; T 2-Wbr continues anteriad from T 2- PWL; T 2-Wbr partial likely due to fluid infilling. T 3-DB runs mediad, dividing after a short distance into T 2-PDLT anteriorly and T 3- DLT posteriad. T 3-VB runs posteroventrad, with a connection to T 2- VLT very close to T 3- S; T 3-VB continues posteriorly as T 3- VLT, linking up with A 1- S. T 2-VLT-Vi on right side, extending past T 3- S into abdomen; unclear if T 2-VLT-Vi links with an abdominal spiracle. T 3- S on right side slightly different from left, possibly due to displacement of tracheae by distended alimentary canal air space; T 3- S on right side with T 3- VLT positioned posteriad as with right side, but with short, curving spiracular branch dorsad and anteriad, with T 2- VLT connecting from anterior; branch continues dorsad to T 2- AWL, T 2-DB, T 2- PWL split as with left side. ABDOMEN: A 1..8- S present. A 1- S modified from subsequent abdominal segments; A 1- S with five branches: A 1-DB, T 3-PWBa, T 3- VLT, and T 3- PL. A 1-DB short and running mediad, connecting with T 3- DLT from anteriad and continuing as A 1- DLT posteriad. T 3-WBr (also partial, likely due to fluid infilling) runs anteriad, continuing with small T 3-W-cu-a into trailing edge of hind wing. T 3- VLT from directly ventrad. T 3- PL runs ventrad, lateral from T 3- VLT, joining with T 3- AL and extending into hind leg as T 3- L. Segments A 2..7 likely similar but morphology difficult to determine due to distention of air-filled alimentary canal. A 2..7- DLT present, arcing slightly dorsad and usually sinuous. A n - VLT present. A 6-VC visible; other A n -VC likely present but displaced against body wall, see figure 78. Several visceral tracheae visible, but dif- ficult to determine morphology; A 3-Vi and A 4-Vi large and directly posteriad, spanning sev- eral segments. A-Cr visible at base of cerci., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Lacombe, D. 1958. Contribuicao ao estudo dos Embiidae. III. Aparelho respiratorio de Embolyntha batesi Mac Lachlan, 1877 (Embiidina). Studia Entomologica 1 (1): 177 - 195.","Lacombe, D. 1971. Anatomy and histology of Embolyntha batesi MacLahlan, 1877 (Embiidina). Memorias do Instituto Oswaldo Cruz 69 (3): 331 - 396.","Szumik, C., M. L. Juarez, M. J. Ramirez, P. Goloboff, and V. V. Pereyra. 2019. Implications of the tympanal hearing organ and ultrastructure of chaetotaxy for the higher classification of Embioptera. American Museum Novitates 3933: 1 - 32."]}

Gryllus sp. “Field cricket” Figure 58 (lateral), 59 (dorsal), 60 (ventral) Plates 35 (lateral), 36 (dorsal), 37 (ventral) The prothorax features a cagelike network referred to as a “pronotal rim” (prt) by Ander, which we interpret here as T 1-DVi. DESCRIPTION: HEAD: Three paired trunks extending into head: H-DCT and H-VCT present, with additional ventral H-VLT branch from prothorax. Head branches highly networked and cagelike, with multiple dorsal-ventral and lateral connections, making assessment of homology challenging. Mouthparts, H-Ant, and H-Oc determined, but remaining tracheae are highly networked and not homologized here. Readers are referred to online digital models for interactive viewing and further research. THORAX: T 2- S positioned just posterior of foreleg with split opening, typical T 2- S dorsal and secondary T 2-VS ventral. T 2- S with four branches: H-DCT, H-VCT, T 2-DB, T 2-VB. H-DCT thick, extending dorsad and medially, curving anteriad and extending into head; T 1-DVi branching laterally and dorsad from H-DCT close to dorsal margin of T 2- S, dividing into cagelike network of T 1-DVi tracheae along pronotal wall. H-VCT with short T 1-Cx running just anteriad of spiracular opening, extending anteriad and ventrally into forecoxa with multiple branches in a cagelike network similar to pronotum. H-VCT extends medially, curving anteriad and extending into head; T 1- AL running ventrad at this curve. T 2-DB runs dorsad, curving medially and ventrad as start of T 2- DLT, T 2- AWL extending laterally and dorsad near this curve, bifurcating into T 2-Wbr posteriad and T 2- AL ventrad, extending posteriorly toward T 3- S; fanlike tracheae extend posteriorly from T 2-DB, likely into flight muscles. T 2-Wbr with T 2-W-c-r branching dorsad into wing, while T 2-Wbr continues ventrad, connecting with T 3-DB. T 2-VB runs ventrad, linking with T 2- VLT; similar to T 2-DB, fanlike flight muscle tracheae extend posteriorly from T 2-VB. T 2- VLT running posteriad, with T 2-VC2 possible. T 1- AL with posterior branch extending into forecoxa and linking with T 2-Cx network; anterior branch running dorsad into prothorax. Multiple expanded visceral tracheae along venter; T 1-VC possible but networked morphology makes homologies uncertain. T 2-VS thick, extending directly mediad as T 2-VC, meeting at midline with circular T 2-Sept present; see figure 61 for internal cut-away view showing medial septum, and figure 62 for ventral view with legs removed for clarity. Large T 1- PL runs dorsad and lateral from T 2-VC, extending into foreleg as T 1- L; T 1- AL and T 1- PL join only via smaller tracheae extending from T 1-Cx network. T 1-L-Ty tympanum present at proximal end of tibia. T 3- S with five branches: T 3-DB, T 3-lvl, T 3-suf, T 2- PL, T 3-VB. T 3-DB runs dorsad, with connection to T 2-Wbr just dorsal of T 3- S; T 3-DB continues dorsally, with T 3- AWL splitting dorsad and slightly lateral; T 3-DB connecting in Y-shaped junction with T 2- DLT from anteriad and T 3- DLT posteriorly. T 3-DB-Vi dorsal, extending posteriad, ending blind with several small tracheae posteriad. T 3- AWL with sharp curve ventrad and laterally, with dorsal branch to T 3-Wbr at apex of curve; T 3-Wbr with small T 3-W-c-r branch posteriad; T 3- AL thin, joining with T 3- PL ventral from A 1- S and continuing as very thick T 3- L. Additional T 3-VL branching laterally from T 3- VLT, extending into hind leg, and joining in multiple-tracheae junction with T 3- L; extremely large T 3-Fm extending dorsad into hind femur; smaller T 3-Fm2 almost linear from T 3-VL along ventral part of hind leg. T 3-VC1 and T 3-VC2 anterior and posterior, respectively, along T 3- VLT. T 3-lvl proceeds medially from T 3-DB for a short distance before splitting into two branches, both joining with T 3- VLT, one anteriad and one more posteriad. T 3-suf running mediad, curving ventrally to connect with T 2- VLT. T 2- PL runs mediad before curving laterally, extending into midleg. T 3-VB extends directly ventrad, connecting to T 3- VLT near T 3-suf connection. ABDOMEN: A 1..8- S present; A 1..2- S modified, remaining A 3..8- S all similar. A 1- S with two additional connections: T 3- PL, running ventrad with connection to thin T 3- AWL before continuing into hind leg; and T 3- PWL, connecting anteriorly from T 2- S. A 1..8-DB present, running directly dorsad from spiracle and leading to A n - DLT, arcing posteriorly to link with subsequent A n -DB. A 1..4- DLT with paired A n -DLT-Vi, wide but flattened, extending medially; anterior A 3,4- DB-Vi smaller. A 5..8- DLT with single A n -DLT- Vi. A 1..8-DC absent; however, a few A n -DLT-DVi with small lateral commissure to opposite side present. A 1..8-VB present, running directly ventrad and mediad, following sternite wall and connecting with straight A n - VLT, spanning length of abdomen. A n -VC absent. Numerous visceral tracheae extending into gut, with many Vi spanning several segments and some connecting spiracles, including A 3-Vi, linking with A 6-Vi on specimen left side. Several visceral branches lie close to others, appearing to join but remaining separate, such as A 3-Vi close to A 8-Vi on right side. Several visceral tracheae are labeled in the plates and figures; readers are directed to the online 3D supplemental models for additional detail. Notably large A-Cr extending from A 8-DB., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Zorotypus hubbardi “Hubbard’s angel insect” Figure 42 (lateral, dorsal) Several Z. hubbardi specimens were collected from Florida. Unlike the other taxa, where specimens were frozen alive, these specimens died during transport and were frozen upon arrival. Likely due to their untimely demise, tracheae suffered from fluid infilling before scanning, resulting in obscured morphology. Several specimens were scanned, and the best example was chosen for inclusion here. Zoraptera are an excellent candidate for further micro-CT study of better-preserved specimens. DESCRIPTION: HEAD: H-DCT and H-VCT in close contact, proceeding anteriad. H-Ant off H-DCT, no other head tracheae visible in this scan. THORAX: T2-S with several branches visible on specimen right side but only two determinable: T2-VB and T2-CT. T2-VB ventrad; T2-VC present. T3-S visible with T3-DLT extending dorsad and posteriorly to link with A1-S. Other thoracic tracheae partial, determined from examining volume cross sections to establish position in the body. ABDOMEN: A1..7-S discernible., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Tachycines asynamorous “Greenhouse camel cricket” Figures 65 (lateral), 66 (dorsal, ventral) Plates 41 (lateral), 42 (dorsal, ventral) A single camel cricket, Tachycines asynamorous, was scanned, but substantial fluid infilling of tracheae resulted in assessing homology of many branches difficult. Although of suboptimal quality, this specimen was included because of its placement within Orthoptera and the relative modifications of the mesothoracic tracheae, specifically how they relate to modifications for sound reception. Identifiable tracheae are labeled and described here but should be considered preliminary. Our mesothorax assessments differ from Ander (1939), particularly with H-DCT and H-VCT. Ander identifies most of the larger tracheae extending into head as multiple branches of H-VCT and the small branch as H-DCT, whereas we have determined the small dorsal branch is T 2-VB, the next ventral branch is H-DCT, followed by H-VCT, which does have a split into H-VCT and a smaller anterior trachea that has T 1- AL ventrad. DESCRIPTION: HEAD: T 1- DLT partially visible and likely extending into head capsule. H-DCT and H-VCT both thick, with dorsal-ventral connection likely but not visible. Several air spaces visible, likely preservational artifacts. H-VCT splits into two branches, large dorsal one and smaller ventral, which proceeds anteriorly with T 1- AL ventrad. THORAX: T 2- S with five branches: T 2-DB, T 2-VB, H-DCT, H-VCT, and T 1- PL. T 2-DB running dorsad and anteriad, extending into head capsule after broad curve along prothorax. H-DCT thick, extending anteriad through prothorax into head capsule. H-VCT splitting into two branches: large dorsal trachea, extending anteriad into head, and a smaller ventral branch, extending anteriad into head with T 1- AL ventrad. T 2-VC not visible but likely present; many ventral thoracic tracheae infilled with fluid. T 2-DB runs dorsad, with T 2- AL branching in hairpinlike turn ventrad into T 2- L. Remaining branches of T 2-DB not visible. T 2-VB partial, with T-shaped intersection with T 2- VLT. H-DCT and H-VCT both large, of similar size, extending into head as described above. T 1- PL running directly ventrad, partial, likely joining with T 1- AL but not visible in this scan. T 3- S branches largely infilled and difficult to differentiate, appearing to include: T 3-DB, T 3-VB, T 3-lvl, T 2- PL, and T 3-suf. T 3-DB partial, with T 3- AWL visible, leading to T 3- AL, dorsad before curving sharply ventrad and posteriorly into hind leg. T 3-VB running ventrad, joining with T 3- VLT. T 3-lvl extending mediad, joining with T 3- VLT, with small branch posteriad connecting with T 3- PL. T 3-suf partial, extending mediad and slightly anteriorly. T 3-VL possibly visible on specimen left side; T 3-VL likely present but infilled. ABDOMEN: A 1..8- S present. A 1- S modified from subsequent abdominal segments, with large ventral T 3- PL branch. A n -VB visible on most segments, leading to partially infilled A n - VLT. A n -DB likely present but infilled and not visible. A n - DLT likewise probably present but not visible, likely infilled. Several visceral tracheae present from all A n - S., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Ander, K. 1939. Vergleichend-anatomische und phylogenetische Studien uber die Ensifera (Saltatoria). Opuscula Entomologica (supp. 2). Lund: Entomologiska sallskapet."]}

FAMILY AESHNIDAE “Hawkers” or “Darners” The adult Aeshnidae has many air sacs arranged throughout the body, with many thoracic air spaces likely for muscle growth. Preliminary estimates indicate that over 50% of the volume of the specimen is air, either tracheal or in air sacs (Herhold et al., in prep.). Many major tracheae lead into and out of large air sacs, both in the thorax and abdomen, such that determining tracheal pathways and assessing homology is challenging. Most notably, the abdomen possesses four paired longitudinal trunks, a condition not seen in any other insect in this study. This unusual morphology of the adult relative to other winged insects suggested that some of these features may be holdovers from the aquatic immature stage, so a naiad was collected and scanned. To facilitate differentiation of tracheae and tracheated air sacs in the plates and figures for the adult, a subset of the air sacs that serve as tracheal pathways are shown in orange and tubular tracheae are shown in yellow, and the specimen body outline in transparent gray (as in other plates and figures). Although the tracheae are presented as if “on top” of the air sacs, they are located deeper inside the body. The inset image in the plates shows all air spaces (tracheae and air sacs) in gray; readers are encouraged to refer to the 3D models in the supplementary digital data, where air sacs, tracheae, and tracheated air sacs can be viewed separately or together interactively. X-ray cross sections from CT scan data indicate the likely presence of flow-directing valves between some air sacs and tracheae in the adult, particularly in the thorax and abdomen (see fig. 29). Air-sac flow-control valves have been documented in Diptera by Wasserthal et al. (2018), and further research into these structures is needed in Odonata.

Forficula auricularia “Common earwig” Figures 47 (lateral), 48 (dorsal), 49 (ventral) Plates 26 (lateral), 27 (dorsal), 28 (ventral) DESCRIPTION: HEAD: H-DCT and H-VCT thick, of similar diameter; H-DCTs curve inward slightly such that left and right tracheae nearly touch before turning laterally outward on entry to head capsule; H-VCTs both proceed straight into head. H-DCT with several branches just anterior of cervix: H-DCC, H-DCT-Dvi, H-Oc, and H-Ant. H-DCC present. H-DCT-Dvi running laterally and dorsad. H-Oc arcing laterally, with several small tracheae extending into eye, then continuing anteriorly and ventrad via H-Oc-Md to link with ventral H-Md. H-Ant extends anteriorly through head into antenna; left side of Forficula as H-Ant-Ft with H-Ft branching off H-Ant near base of antenna; H-Ft branches off H-VCTsourced H-Md on right side. H-Ant with multiple tracheae in Anisolabis; likely present in Forficula but not visible in this scan. H-VCT likewise with several branches just anterior of cervix: H-VCTVi, H-VC, and H-Mx-Md. H-VCT-Vi running laterally and ventrad, like dorsal trachea. H-VC branches directly from H-VCT. Both H-VC with H-VC-Dvi run directly anteriad, extending as far as frontal area. H-Ft-Lbr absent. H-Mx-Md running anteriad and slightly laterally, with several branches: H-Lbm runs ventrad, with short H-LbmPlp; H-Mx running ventrad, with short H-MxPlp. Remaining H-Md branch runs anteriad, with H-Oc-Md connection from H-DCT; H-Md-Ant branching dorsally on right side to join H-Ant from H-DCT; H-Ft branching from H-Md on right side. THORAX: Distance between T 2- S and T 3- S much shorter in F. auricularia (See fig. 43). ABDOMEN: Abdominal tracheae of F. auricularia consistent with description of overall dermapteran tracheae above except for direction of visceral tracheae. A 6..7-VLT-Vi similar to their anterior counterparts, except A 6..7-VLT-Vi extend posteriorly rather than anteriorly, and do not extend beyond segment boundaries; A 5- A 6 appears to be dividing line for visceral tracheae from median longitudinal trunk, where A 2..5- VLT-Vi tracheae extend anteriorly and A 6..7- VLT-Vi extend posteriorly. A 2..7-VLT-Vi not bilaterally symmetric; right side tracheae larger in cross-sectional area than left. Right side tracheae, while extending into body, also do not supply exact same areas/organs as those from left side. A 3-DLT-Mvi and A 4-DLT-Mvi on left side extend directly toward the posterior, with A 3-DLT-Mvi ending near A 7-DB. A 3-DLT-Mvi on right side much reduced from left side counterpart, extending posteriorly as far as A 4. A 4-DLT-Mvi highly modified; after extending toward the middle of the body, continues well into A 8 and A 9, where it turns toward body wall in large arc that results in trachea pointing anteriorly. A 4-DLT-Mvi with similar loop on right as on left, but much shorter, with apex of loop reaching as far as A 5-DB. Extensive branching/tracheation in A 7 and A 8 for cercal (forceps) muscles., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Medauroidea extradentata “Vietnamese walking stick” Figures 91, 92 (lateral, anterior, posterior); 93, 94 (dorsal, anterior, posterior); 95, 96 (ventral, anterior, posterior) Plates 55 (lateral), 56 (dorsal), 57 (ventral) Although Strauss (2021) conducted the most recent work on stick insect tracheae, he focused on the prothorax and prolegs, concentrating on hearing. He employed terminology from Ander (1939), also incorporated here, although he left several branches unlabeled. In the Medauroidea scan here, T 1- AL and T 1- PL remain separate, at least as far as the distal end of the foretibia. Strauss indicates foreleg (and mid- and hind leg) adaptations for hearing; these cannot be verified from this scan. Medauroidea is a good example of assessing homology using secondary criteria (serial homology). The T 2-DB branching pattern posteriorly in Medauroidea is somewhat ambiguous, in particular the placement of T 2- AL and T 2-Wbr. T 2- AL and T 2-Wbr could be swapped; however, the decision that the dorsal one is T 2- AL is based on serial homology with T 3. Additionally, the shorter DB branches, such as T 3-DB and T 3-VB here in Medauroidea (but also applicable elsewhere), could be argued to be branching directly from the spiracle. The presence or absence of a spiracular “atrium” is not specific here; these structures are most prominent in groups such as Orthoptera, where a large “cavity” sits just inside the spiracle with multiple tracheae branching in various directions. In Medauroidea, it appears that a very short “stub” of DB or VB may have trachea branching from it. T 2- CT may be present, but this stub may also be a spiracular atrium, as the closest (phylogenetically) relative with T 2- CT is Plecoptera (rather distant). The tracheal branching in first abdominal segment is very unusual and assessing its homology calls for some explanation. A 1- DLT is quite clearly absent, as no tracheae arc posteriorly in the form of a DLT; T 3- DLT connects directly to the dorsum of A 1- S with no continuation. A 1- VLT initially appears to be A 1-MLT, but the ventral branch of T 3-VL into the hind leg is indicative of it being a VLT, not MLT. Additionally, A 1-VC branches from T 3-VL, rather than A 1-VB, an unusual arrangement. This branch is not a section of A 1-VB, as A 1- VLT connects A 1- S and A 2- S. The remaining branches are typical. The second abdominal segment is also slightly modified from the remaining segments extending posteriad. A 2-DB and A 2-VB are basically absent—while A 2-DC and A 2-VC are present, they branch directly from A 2- DLT and A 2- VLT. The primary connection between A 2- S and A 1- S anteriad is A 1- VLT. A 2-DC extends a little anteriad of A 2- S; A 2-DC could arguably be A 1-DC but the branching pattern is from A 2- DLT, so homologizing based on connectivity or branching pattern seems more reasonable. DESCRIPTION: HEAD: The head tracheal morphology of M. extradentata features a network of loops interconnecting both dorsoventrally and laterally. Exploration of the 3D models in the supplementary digital data is encouraged. Three sets of tracheae into head: H-DCT, H-VCT, and additional H-VLT. H-DCT dorsad, proceeding anteriorly and forming a prominent H-DCTVLT-Loop anteriad and ventrad, connecting directly with H-VLT. H-Lbm anteriad from ventral apex of H-DCT-VLT-Loop. H-VCT runs anteriad, dividing into H-Ant and two branches, one looping posteriad to connect with H-VCT, forming H-Ant-Loop; second branch looping ventrad and posteriad to join H-VLT. THORAX: T 2- S with four connections: possible T 2- CT, T 2-DB, T 2-VB, and T 1- PL. T 2- CT short and running directly anteriad, bifurcating into H-DCT and H-VCT near posterior margin of prothorax; as T 2- CT absent in other Phasmatodea, this T 2- CT is possibly a deeper spiracular atrium rather than T 2- CT. H-DCT runs anteriad, extending through prothorax into head. H-VCT anteriad, with T 1- AL splitting off into foreleg; short connection to T 1- VLT at this branching point. T 2-DB runs posteriad, curving slightly ventrad before splitting into two pairs: T 2- DLT / T 2- AL dorsal branch and T 2-Wbr/ T 2-lvl ventral branch; T 2- AWL notably absent. For dorsal T 2- DLT / T 2- AL pair, T 2- DLT as with other specimens, positioned along dorsum with connection posteriad to T 3-DB; T 2- AL extending posteriad, connecting with T 3- S via T 2-PWB. Ventral T 2-Wbr/ T 2-lvl pair with T 2- AL posteriad with shallow arc dorsad to connect with T 2- PWL; T 2-lvl along venter, connecting with T 3- S via T 2- VLT connection just anteriad of T 3- S. T 2-VB short and directly ventrad, linking with T 2- VLT posteriad and T 1- VLT anteriorly. Both T 1-VC and T 2-VC present. T 1- PL runs anteriad, linking with T 1- VLT via short T 1-VL; T 1- PL extends into foreleg without joining T 1- AL. T 1- AL and T 1- PL do not join and remain separate at least until the distal end of the foretibia. Two small, visceral medial A 1-DVi-Med and A 1-VVi-Med extend through mesothorax, originating at A 1- S and extending into head. T 3- S with four branches: T 2- VLT, T 3-DB, T 3-VB, and T 2- PL. T 2- VLT from anterior, connecting T 2- S to T 3- S. T 3-DB short and mediad, quickly branching into T 3- AL posteriorly and remaining T 3-DB dorsad; T 3-DB joining with T 2- DLT anteriorly and T 3- DLT posteriorly in Y-shaped junction, linking to T 2- S and A 1- S. T 3- AL posteriad, joining with T 3- PL to form T 3- L, extending into hindleg. T 3-VB short, similar to T 3-DB, quickly splitting into T 3- VLT posteriad and remaining T 3-VB ventrad. T 3- VLT runs directly posteriad to A 1- S; T 3-DC present toward posterior margin of metathorax. T 3-VB continues to T 3-PVC, which forms posteriad segment of hexagonal network comprised of T 3-VC anteriad and lateral sections connected to T 2- VLT. T 2- PL anteriad, joining T 2- AL and extending into mideg. T 2-VL branching from T 2- VLT, also extending into midleg; T 2-VL and T 2- L remain separate to distal end of midleg tibia. A 2-DVi-Med and A 2-VVi-Med extending through metathorax, with laterally asymmetric connections: A 2-DVi-Med to T 2- VLT on specimen’s left side, A 2-DVi-Med to T 2- VLT on specimen’s right side. ABDOMEN: A 1..8- S present. First abdominal segment approximately half as long as remaining abdominal segments. A 1- S and A 2- S branching patterns highly modified from remaining abdominal segments. A 1- S with four branches: T 3- DLT, A 1- VLT, T 3- VLT, and A 1- PL. A 1- S with additional A 2-VVi-Med connection on left side only, see description of A 2-VVi-Med below. T 3- DLT runs dorsad, connecting in anterior arc from T 3- S; A 1- DLT notably absent. A 1- VLT runs directly posteriad to A 2- S; T 3-VL directly ventrad from A 1- VLT; A 1-PVC branching from T 3-VL. T 3- VLT from anterior, with two ventral commissures A 1-AVC1 and A 1-AVC2. T 3- PL ventrad, linking with T 3- AL before arcing posteriad to extend into hind leg. A 2- S with seven branches: A 1- VLT, A 2-DVi-Med, A 2-VVi-Med, A 2- DLT, A 2-DVi, A 2-VVi, and A 2- VLT. A 1- VLT runs directly anteriad from A 1- S. A 2-DVi-Med beginning as sinusoidal, looping branch, extending anteriorly and medially, each side combining in Y-shaped junction in metathorax and proceeding anteriorly along venter; A 2-DVi-Med asymmetric, with sinusoidal form on both sides but only right side leading to Y-shaped join, with left side coming from A 1- S. A 2-VVi-Med similar, arranged along venter. A 2- DLT runs dorsad and posteriad in arc connecting to A 3- S; A 2-DC present off A 2- DLT. A 2-DVi and A 2-VVi ventrad, connecting with A 3- S. A 2- VLT likewise in ventral arc, also connecting with A 3- S; four tracheae connect A 2- S with A 3- S. Remaining A 3.. A 8 segments similar, with varying degrees of A n -DB; A 3-DB short, A 4-DB not present, etc. A n - DLT and A n - VLT present on all, connecting segments longitudinally. A 3..8- S with anteriad visceral tracheae generally dorsad, posteriad visceral tracheae generally ventrad. A 4-Vi-VC present, formed from visceral tracheae and not from VLT as is typical., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Strauss, J. 2021. The tracheal system in the stick insect prothorax and prothoracic legs: homologies to Orthoptera and relations to mechanosensory functions. Arthropod Structure & Development 63: 101074.","Ander, K. 1939. Vergleichend-anatomische und phylogenetische Studien uber die Ensifera (Saltatoria). Opuscula Entomologica (supp. 2). Lund: Entomologiska sallskapet."]}

Ephemera sp. “Burrowing mayflies” Figures 22 (lateral), 23 (dorsal, ventral) Plates 11 (lateral), 12 (dorsal), 13 (ventral) Ephemera sp., a much larger species at approximately 1 cm body length, was scanned at 13.1 µm voxel size, lower resolution than the two baetid specimens at 2.3 µm and 4.1 µm. Smaller abdominal visceral tracheae visible in the baetid scans are likely present in Ephemera but not visible at the scanned resolution. DESCRIPTION: HEAD: Two H-DOc: H-DOc1 extending from H-Ocel, H-DOc2 from H-DCT. H-Ant barely visible in this scan, likely due to lower resolution. THORAX: T 1-VVi originating from H-DCT on left side; T 1-VVi1 from H-DCT and T 1-VVi2 from H-VCT on right side., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

ORDER MANTODEA The tracheal system of mantises in part has been examined in detail since the discovery of the ventrally located “cyclopean” ear by Yager and Hoy (1986). More recent investigations have used micro-CT based methods (Wipfler et al., 2012); however, a complete mapping of mantis respiratory systems has been lacking. Two specimens are included here: the common Chinese mantis Tenodera sinensis and the popular “Devil’s flower mantis,” Idolomantis diabolica. Tenodera is described here in detail but the somewhat more complex Idolomantis is covered only broadly; 3D models are included in the supplementary digital data for further research. The morphology of H-DCT and H-VCT deserves special note here. Nominally, branching patterns starting at spiracle are judged to be more stable, as spiracles are used as the landmarks for assessing homology (as discussed above). The tissues supplied in the mantis prothorax and head, however, indicate a dorsal/ventral swap of H-DCT and H-VCT. For H-VCT in all other taxa, T1-AL branches ventrally from H-VCT in the prothorax. In Mantodea, however, this branch (H-VCT) begins dorsally at T2-S, and then flips position with the other cephalic trachea at the anterior end of the pronotum and retains the condition of T1-AL extending ventrally. The length of the prothorax in mantises likely plays a role in this dorsal-ventral reversal, but the reasons are unclear. An alternative interpretation is that one of these trunks is T2-CT and splits into H-DCT and H-VCT in the prothorax, in conjunction with dorsal-ventral connections in the head. However, this would also imply that T1-PL splits from T2-CT, a condition not encountered in any specimen. Looking toward the posterior end of the thorax, T3-DLT is unusual in that it skips a connection to A1-S, extending from T3-S posteriad to A2-S via A2-DB; A2-DLT continues posteriad as with other taxa. Also curious is T2-PWL branching from T2-PL and connecting with T2-AL. This is similar to what is seen in T 3 in Orthoptera but appears to be present here in the midleg. The mesothorax is shorter anteriorposteriorly in Orthoptera, so perhaps this condition is either difficult to discern or simply not present. Another modified branching pattern is T3-VL branching from directly from A1-VC rather than VLT. While the origin (VLT) of T3-VL here is unusual, its extension into the leg and overall pattern appears homologous with T3-VL elsewhere.

Calopteryx maculata “Ebony jewelwing” Figures 38, 39 (lateral, anterior, posterior), 40 (dorsal), 41 (ventral) Plates 21 (lateral), 22 (dorsal), 23 (ventral) A single damselfly was scanned at 19 µm, which should have been sufficient to capture details of abdominal tracheae; however, this specimen was frozen to -20° C early in the study. As small tracheae were likely infilled, this specimen is not described in detail, but three-dimensional models are included in the online supplementary digital data. The thoracic tracheae appear to be very similar to the aeshnid, along with extensive air sacs. 62 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 459 It is unclear whether there are four paired abdominal trunks as in the dragonfly, but it seems likely. Further studies should focus on Zygoptera in addition to more dragonfly specimens to verify and solidify tracheal patterns in the flight motor and abdomen., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Trigoniophthalmus alternatus “Jumping bristletail” Figures 8 (lateral), 9 (dorsal, ventral) Plates 1 (lateral), 2 (dorsal), 3 (ventral) Trigoniophthalmus, as the representative of the most basal order in Class Insecta, is notable in its tracheal architecture by a complete lack of longitudinal connections between spiracles. This taxon is critical to understanding the apparent insect ground-plan tracheal structure. The thoracic tracheae of most taxa are supplied by both T 2- S and T 3- S, with T 2- DLT connecting longitudinally. In Trigoniophthalmus, however, T 3- S appears to only supply T 3- L and its associated coxa. Branches from T 2- S extend posteriorly into the metathorax, nominally supplied by T 3- S, including an apparent T 3- DLT. The naming of T 3- DLT here is an instance of using the positional criterion in homology (sensu Remane, 1952), in that the connectivity of this trachea is not consistent with other taxa; however the position suggests its identification as T 3- DLT (de Pinna, 1991). T 2-VB extends posterior, almost in the opposite direction of the anterior-reaching cephalic branches. While the position of T 2-VB may not appear to be “ventral” in nature, a comparison of its relative position in the hump-backed Trigoniophthalmus and in particular its connection to T 2- L with apterygote taxa from Zygentoma and Dermaptera demonstrates its homology as a ventral branch. Several tracheae range anteriorly or posteriorly beyond segment boundaries, most prominently A 5-DB-DVi, which extends posteriorly past A 6- S, reaching A 7- S; and A 7-Cr, which likewise extends posteriorly from A 7- S into both the cerci and terminal filament. However, tracheae for most segments, particularly in the abdomen, remain restricted to their individual segment, placing Trigoniophthalmus among the simplest tracheal body plans in this study and unique in its lack of longitudinal connections. This corroborates observations made by Palmén (1877) and reviewed by Dittrich and Wipfler (2021). DESCRIPTION: HEAD: Characteristically arched thorax, pronotum covering much of head, making boundary between thoracic tracheae and head tracheae rather indistinct. T 2- S at anteriormost margin of mesothorax, covered by overhanging tergum, shown in figure 10. H-DCT very thick, with three branches: H-Ic, extending anteriorly and dorsad; H-Oc-Ant anterior and medially before dividing into H-Oc toward midline and H-Ant laterally; H-Mx proceeds anteriad with H-MxPlp branching ventrally and anteriad. H-VCT very thick, with two branches: H-Lbm ventrad, extending into H-LbmPlp; H-Md anteriad, crossing over H-Md from opposite side of head but not connecting. THORAX: T2-S present, with five tracheae: H-DCT and H-VCT leading anteriad directly into head, beginning at T2-S and running parallel for length of prothorax; T2-DB leading dorsad; T2-VB and T2-L directly posteriad. H-DCT with no thoracic branches; H-VCT with T1-L branching ventrally; T1-VC present, extending from T1-L. T2-DB-Vi branches just dorsal of T2-S, extending anteriorly; T2-DB continuing dorsad, dividing into what appear to be anterior T1-DLT and posterior T2-DLT near midline; T1-DLT and T2-DLT extend into viscera with no connections to neighboring spiracles. T2-L running posteriad and ventrally, into midleg; large T2-L-Vi and smaller T2-VC divide from T2-L posterior from T2-S. T2-VC joins with anterior-arching T3-VC to form T2-VX intersection. T2-L-Vi extends posteriad into metathorax, with apparent dorsal T3-DLT, T3-Cx ventral, and numerous small visceral tracheae. T3-S ventral to and much smaller than T2-S, with two tracheae: T3-L and T3-VB. T3-L extending dorsad with small T3-L-Vi before arcing ventrad into hind leg; T3-VB directly toward midline with small T3-VC branch that arcs anteriorly to join T2-VC at T2-VX. ABDOMEN: A1..7-S present, all located ventrally. No longitudinal connections present; figure 11 with representative abdominal segment. A n -S with A n -DB running dorsad along arc of body wall, turning inward toward midline of body but not forming DC; A n -VB branching dorsally for a short distance before arcing ventrad toward midline. A n -VC absent. A n -DB with visceral tracheae A n -DB-MVi, branching anterior and medially halfway up body; A n -DB-DVi branches dorsally toward tergal wall. A5-DB-DVi extends posteriorly to 8th abdominal segment; A7-DB-DVi extends posteriorly past 8th abdominal segment, dividing into A-TF and A-Cr; neither A 5-DB-DVi nor A 7-DB-DVi connect to spiracles of other segments. A-TF with two tracheae per side (4 total); A-Cr single trachea per cercus., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Remane, A. 1952. Die Grundlagen des naturlichen Systems, der vergleichenden Anatomie und der Phylogenetik. Leipzig: Geest & Portig.","de Pinna, M. C. C. 1991. Concepts and tests of homology in the cladistic paradigm. Cladistics 7: 367 - 394.","Palmen, J. A. 1877. Zur Morphologie des Tracheensystems. Leipzig: Wilhelm Engelmann.","Dittrich, K., and B. Wipfler. 2021. A review of the hexapod tracheal system with a focus on the apterygote groups. Arthropod Structure and Development 63: 101072."]}

Timema cf. californicum “ California timema (walkingstick)” Figures 79, 80 (lateral, anterior, posterior); 81, 82 (dorsal, anterior, posterior); 83, 84 (ventral, anterior, posterior) Plates 49 (lateral), 50 (dorsal), 51 (ventral) The tracheal morphology of Timema is nota- ble for the proliferation of comparatively thin tracheae that form networks throughout the body. These networks make assessment of homology difficult especially in the thorax, where differentiating similarly networked tracheae from other taxa is unclear. Identifiable homologous tracheae are labeled here, and incorporation of data from some of the 20 or so other Timema species could help to resolve ambiguous structures. Notably, T 2,3- DLT are absent in Timema, with the additional absence of the corresponding T 2,3-DB; however, the networked nature of tracheae elsewhere likely compensates for the lack of dorsal longitudinal connections. Although distantly related, the Timema thorax is rather reminiscent of termites, with (possibly) dual ventral commissures, which may be convergent. DESCRIPTION: HEAD: Head tracheae with several networked interconnections dorsoventrally; due to three-dimensional nature of head tracheal architecture, readers are encouraged to refer to models in supplementary digital data. Prominent H-DCT-VCT-Loop at anterior margin of prothorax, with smaller H-DCT and H-VCT branching from dorsal and ventral portions of loop. H-DCT extending anteriad and slightly dorsad, splitting into dorsal branch to H-DX intersection near vertex; and anteriad H-DCT-Ant branch, joining with ventral H-VCT-Ant branch and extending into H-Ant. H-DX with anteriad branches extending laterally and ventrad, reconnecting with H-VCT-Ant as H-DX-VCT-Loop. H-VCT runs anteriad, with H-VCT-Ant branching anterodorsally to join with H-DCT-Ant. H-VCT continues anteriad with H-Mx branching ven- trad; H-Mx with H-VC before branching to H-MxPlp. H-VCT with continued anterodorsal curve, with H-Md branching anteriad; H-VCT joining with H-DCT via H-VCT-Ft-Loop; H-FtLbr branching ventrad near anterior apex of H-VCT-Ft-Loop. THORAX: T 2- S with three branches: H-DCT, H-VCT, and T 2- AWL. H-DCT runs directly anteriad toward head; small T 1-Cx ventrad in middle of prothorax. H-VCT likewise running anteriad, with T 1- AL ventrad at posterior margin of prothorax; T 1- PL not present. T 1- AL with medial branch to T 1-VX. T 1-VX branching into three anteriad tracheae, extending toward head as H-VLT, with right side H-VLT fusing with H-VLT-Med anteriad of cervix. T 2- AWL runs ventrad and mediad before turning dorsally and posteriad in an S-shaped curve; small T 2-DB and T 2-VB branching dorsad and ventrally (respectively) from T 2- AWL. T 2-DB linking with apparent T 1- DLT anteriad; T 2- DLT not visible. T 2-VB runs ventrad at bottom of T 2- AWL S-curve, bifurcating into anterior and posterior branches, both leading to network of tracheae forming numerous ventral commissures. Remainder of T 2- AWL bifurcating into T 2-Wbr and T 2- AL; T 2-Wbr directly posteriad, linking with T 3- S via T 2- PWL; T 2- AL posteriad and ventrad, linking with T 2- PL and extending into midleg. T 3 with three branches: T 2- PWL, T 3- AWL, and T 3-VB. T 2- PWL runs anteriad, splitting into T 2-Wbr dorsally and T 2- PL ventrad; T 2- PL joining with T 2- AL and extending into midleg. T 3- AWL runs dorsad, curving posteriorly and splitting into T 3-Wbr posteriad and T 3- AL ventrad; T 3- AL joining with T 3- PL and extending into hind leg. T 3-VB splitting into four tracheae close to T 3- S; at least two of these extending into network of ventral commissures; several X-shaped commissure intersections present. ABDOMEN: A 1..8- S present, short A n -SB spiracular branch present on all A 1..8- S. A 1- S branching pattern slightly modified from remaining A 2..8- S, with T 3- PWL running anteriad, splitting into T 3-Wbr anteriad and T 3- PL ventrad, with T 3- PL joining with T 3- AL and extending into T 3- L. A 1..8-MLT present, with A 1..5-DB branching dorsad from A n -MLT; A 6..8-DB branching directly from A 6..8-SB. All A 1..6-DB linking with thin, sinuous A 1..6- DLT along dorsum; A n -DC not present. A 7,8- DLT substantially larger, with fanlike morphology expanding into highly tracheated hind- and midgut “appendices” (Shelomi et al., 2015). A 1..8-VB present, extending to link with sinuous A n - VLT along venter; A 2,3,6,7,8-VC present; given distribution, other A n -VC likely present but not visible. Numerous visceral tracheae, most notably forming asymmetric connectives A 4- A 5-Vi-AsymC and A 5- A 6-Vi-AsymC; A 7-Vi-VC also present., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Shelomi, M., I. R. Sitepu, K. L. Boundy-Mills, and L. S. Kimsey. 2015. Review of the gross anatomy and microbiology of the Phasmatodea digestive tract. Journal of Orthoptera Research 24 (1): 29 - 40."]}

FAMILY BAETIDAE Two baetids were scanned to investigate developmental changes. These are two separate specimens, not the same specimen scanned twice, as done in beetles by Lehmann et al. (2021). Tracheal morphology between subimago and adult is strikingly consistent, apart from the single alimentary air sac in the adult (vs. divided in subimago), indicating that tracheal development is essentially complete by the subimago stage., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Lehmann, P., M. Javal, A. D. Plessis, and J. S. Terblanche. 2021. Using microCT in live larvae of a large woodboring beetle to study tracheal oxygen supply during development. Journal of Insect Physiology 130: 104199."]}

ORDER ORTHOPTERA Orthopteran anatomy (and some tracheae) has been diagrammed in classic works, but the first proper treatments of respiratory systems were by Vinal (1919: for Dissosteria carolina), Carpentier (1927: for Phasgonura viridissma), and Ander (1939: for Ensifera in general). Several tracheal terms were introduced using Orthoptera, particularly those involving auditory adaptations and saltatorial legs, and the work of these researchers (particularly Ander) was instrumental in mapping the tracheae here. More modern studies have focused on physiology, including ventilation in Schistocera gregaria in influential experimental works by Miller (1960a, 1960b, 1960c), active tracheal compression in Orthoptera observed via synchrotron imaging by Westneat et al. (2003), and the distribution of air spaces in Schistocera americana by Shaha et al. (2013). Four orthopteran specimens were scanned: Gryllus sp. (Gryllidae), Romalea microptera (Romaleidae), Tachycines asynamorous (Raphidophoridae), and a Meconema thalassinum (Tettigoniidae). Orthoptera tracheal morphology is best represented here in the scans of Gryllus and Meconema, and these are described here in detail. Notable features are described for the remaining specimens, but they are presented in a more basic manner due to the suboptimal quality of the scan of Tachycines and the substantial complexity of Romalea. The most comprehensive work to date on tracheal morphology of Orthoptera is by Ander (1939). His work formed the basis for many of the homology statements here, although we reinterpret some of his tracheae, in particular the supraventral (suv) in the prothorax and mesothorax. Ander indicates that the suv is absent in the metathorax in all Ensifera (his fig. 81). Interestingly, Ander cites Carpentier (1927) as the source for supraventral, where it does not go into the leg (Carpentier’s figure 3). However, Ander’s figure 83 details Gryllidae (fig. 81 is his overall view of Ensifera) and identifies three tracheae going into the proleg: pa, pp, and suv (supraventral), an apparent departure from Carpentier’s suv. Herein, T n -AL refers to Ander’s pa, T n -PL for pp, and T n -VL for pve. (Refer to table S 1 in the online supplement for all reassignments of labels and terms from previous studies.) Ander’s suv, more consistent than Carpentier’s, is likely T1-Cx (and even T1-PL in some taxa), designated here as such. Ander’s suf (suprafurcal), lvl (lateral lateroventral), and pf (postfurcal connective, apparently absent in Gryllus but present in other Ensifera) tracheae were not found to be homologous outside Orthoptera. His terminology is retained for descriptions of Orthoptera for convenience. The dorsum of the metathorax in both Gryllus (Gryllidae) and Meconema (Tettigoniidae) both possess T3-DB-Vi, paired air sacs reminiscent of a root vegetable, and ending blind (fig. 59, pl. 36). These tracheae are similar in morphology to those found in the ventral thorax of Dictyoptera for hearing, and their possible function as such should be investigated further.

Tenodera sinensis “Chinese mantis” Figures 97, 98 (lateral, anterior, posterior); 99, 100 (dorsal, anterior, posterior); 101, 102 (ventral, anterior, posterior) Plates 58 (lateral), 59 (dorsal), 60 (ventral) DESCRIPTION: Pronotum, metathorax, and anterior portion of abdomen with air-filled spaces, likely alimentary canal and transient as not connected to tracheae (see fig. 103). HEAD: Tracheae leading to appendages are labeled; however, the head of Tenodera features a complex network of intersecting tracheae and air sacs. Readers are encouraged to review the 3D models in the supplementary digital data. THORAX: Thorax with numerous elongate, bandlike visceral tracheae throughout, often obscuring views. Exploration of 3D models in digital supplementary data is encouraged. T 2- S positioned posterior to characteristically elongate pronotum, with four branches, crowded close together: T 2-DB, T 2-VB, H-DCT, H-VCT. T 2-DB runs mediad and slightly dorsad, with split off to T 2- AWL posteriad; T 2-DB continues briefly before joining T 1- DLT anteriad and T 2- DLT posteriad in Y-shaped junction. T 2- DLT running in shallow arc ventrad, with unusual condition of linking with T 3- S via connection to T 2- PL. T 2- AWL arcing dorsally and posteriad, with T 2-Wbr branching dorsad at apex of curve; T 2- AWL continues as T 2- AL, extending posteriad into midleg; T 2-Wbr with dorsad T 2-W-c-r branch, remaining T 2-Wbr connecting to T 2- PWL from T 3- S. T 2-VB short, running directly anteriad, bifurcating into T 1- PL anteriad and T 2- VLT posteriad; T 2-VC likely present off T 2- VLT; T 1- PL extending through mesothorax and prothorax with ventral curve into foreleg at base of forecoxa. T 2-VL branching close to origin of T 2- VLT, extending straight through coxa into midleg. H-DCT beginning ventrad and H-VCT dorsad, opposite of usual arrangement; both tracheae extending directly anteriad, switching dorsoventrally to typical positions at anterior margin of mesothorax. (See Discussion section for homology assessment of these tracheae.) H-VCT with T 1- AL running ventrad just anterior of dorsoventral H-DCT/H-VCT switch. T 3- S with n connections: T 3-DB, T 3- AWL, T 3-VB, T 2- PWL. T 3-DB mediad, curving dorsally and posteriad as T 3- DLT, connecting directly to A 2- S with no connection to A 1- S; A 1-DB absent. T 3- AWL runs just lateral of T 3-DB, arcing posteriad, with T 3-Wbr branch; remaing T 3- AWL continuing as T 3- AL into hind leg. T 3-Wbr with T 3-W-c-r, continuing posteriad to connect to A 1- S via T 3- PWL. T 3-VB runs ventrad and posteriad, connecting with A 1- S via T 3- VLT; T 3-VL branching from T 3- VLT close to T 3- S. T 2- PWL short, extending anteriad, splitting into T 3- PL ventrad and T 2-Wbr anteriorly. Metathorax with several networked visceral tracheal branches, especially along venter; most notable is T 3-Ty for hearing. (Additional tracheae of unknown homology enter the legs, similar to Blattodea [roaches], which require further investigation.) ABDOMEN: A 1..8- S present and functional. A 1- S connections atypical from remaing spiracles; A 1- S with only two connections: T 3- PWL and A 1-VB. A 1-DB absent; A 1-MLT possible but not discernible in this scan. T 3- PWL runs from anterior, linking with T 3- S via T 3-Wbr. A 1-VB ventrad, following sternite, forming A 1-VC; T 3- VLT joining with A 1-VB, A 1- VLT extending posteriad from T 3-VC. T 3-VL branching from A 1-VC. Remaining A 2..8- S connections largely similar, with A n -DB extending dorsad, joining with A n - DLT; A n -MLT extending anterior-posteriorly through length of abdomen; and A n -VB ventrad, joining with A n - VLT. Nearly all tracheae bandlike, with visceral branches throughout abdomen. A 4- S and A 5- S with numerous sinusoidal visceral tracheae., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

ORDER BLATTODEA Three roaches were scanned during the study: the common American cockroach Periplaneta americana, the popular Madagascar hissing cockroach Gromphadorhina portentosa, and Blaptica dubia. The tracheal system of Gromphadorhina has been studied via dissection to determine the physiology of its hissing behavior (Nelson, 1979; Nelson and Fraser, 1980) and was micro-CT scanned in a demonstration of semiautomated segmentation techniques (Lösel et al., 2020). Active tracheal compres- sion in Blattodea was studied via synchro- tron imaging by Westneat et al. (2003). Periplaneta is described here in detail. As with other complex specimens, the other two roaches, Gromphadorhina and Blaptica, are only briefly described. Readers are directed to the labeled 3D models in the supplemen- tary digital data for further investigation.

ORDER DERMAPTERA Dermaptera have been the subject of recent micro-CT studies, including the discovery of active tracheal compression via synchrotron imaging (Westneat et al., 2003) as well as a detailed analysis of the head of Forficula auricularia (Neubert et al., 2017). Dermaptera phylogeny is considered to be generally unresolved, with distinctions between lower Dermaptera and higher Dermaptera considered somewhat arbitrary (Haas, 2018). Recent transcriptomic and morphological studies have refined relationships within Dermaptera (Wipfler et al., 2020); however, these analyses omit the fossil record (Tihelka et al., in prep). The taxa here consist of one “lower” dermapteran (Anisolabis maritima, Anisolabidae, female) and one “higher” (Forficula auricularia, Forficulidae, male), and although Anisolabis lacks wings, they are alike in tracheal architecture. Sex was determined for both species based on sexual dimorphism of the cerci. While the specimens were scanned at similar resolutions, 11.6 mm 3 /voxel for Anisolabis and 13.5 mm 3 /voxel for Forficula (see table 3 for all scan parameters), substantially more visceral tracheae are visible in the Anisolabis scan. This may be the result of slightly higher resolution, but also possibly due to different scanning parameters or preservation artifacts (fluid filling of small tracheae postmortem). Regardless, sufficient detail is present in both specimens to assess tracheal homology. The two dermapteran specimens are similar in their overall tracheal layout, with most differences in the heads. Wing base tracheae T2,3-Wbr are well-developed in Anisolabis, even though apterous; however, wing tracheae T2,3-W-c-r and T2,3-Wcu-a are absent. A1-S is positioned dorsally in both specimens, unlike the remaining abdominal spiracles, possibly a modification for the ability of earwigs to raise the abdomen dorsally and forward to use the forceps for predation and defense. Additionally, the A n -VLT-Vi in Anisolabis all proceed anteriorly, whereas in Forficula, there appears to be a “split” where A n -VLT proceeds anteriorly for A2..5-VLT-Vi..5, but posteriorly for A6..7-VLT-Vi. DESCRIPTION: HEAD: Majority of tracheal structures similar between Anisolabis and Forficula, differences described here for comparative clarity. H-DCT and H-VCT of similar diameter; H-DCTs curve inward slightly such that left and right tracheae nearly touch before turning laterally outward on entry to head capsule; H-VCT proceeds straight into head. H-DCT with several branches just anterior of cervix: H-DCC, H-DCT-DVi, H-Oc, and H-Ant. H-DCC present. H-DCT-Dvi running laterally and dorsad. H-Oc arcing laterally, with several small tracheae extending into eye, then continuing anteriorly and ventrad via H-Oc-Md to link with ventral H-Md; H-Oc-Ant branches off H-Oc in Anisolabis into antenna. H-Ant extends anteriorly through head into antenna; left side of Forficula as H-Ant-Ft with H-Ft branching off H-Ant near base of antenna. H-Ant with multiple tracheae in Anisolabis; likely present in Forficula but not visible in this scan. H-VCT likewise with several branches just anterior of cervix: H-VCT-Vi, H-Ft-Lbr (absent in Forficula), H-VC (off H-Ft-Lbr in Anisolabis), and H-Mx-Md. H-VCT-Vi runs laterally and ventrad, like dorsal trachea. In Anisolabis, H-Ft-Lbr runs anteriad, with H-VC extending medially to link left and right sides; H-Ft branching laterally and anteriad with H-Lbr directly anteriad. In Forficula, H-VC branching directly from H-VCT. Both H-VC with H-VC-Dvi running directly anteriad, extending as far as frontal area in Forficula. H-Ft-Lbr (absent in Forficula) running anteriad, with small H-Ft splitting laterally and anteriad, remaining H-Lbr anteriad. H-Mx-Md runs anteriad and slightly laterally, with several branches: H-Lbm running ventrad, with short H-LbmPlp; H-Mx ventrad, with short H-MxPlp. Remaining H-Md branch runs anteriad, with H-Oc-Md connection from H-DCT; H-Md-Ant branching dorsally (absent in Forficula left side) to join H-Ant from H-DCT. THORAX: Although the thoraces of Anisolabis and Forficula differ substantially in overall exterior morphology, as seen in figure 43, the tracheal topology of the thorax is retained between the two taxa. T2-S with four tracheae: H-DCT, H-VCT, T2-AWL, T2-DB; T2-CT absent. H-DCT arcs mediad before proceeding anteriorly; T1-Dvi branching close to T2-S, extending anteriad with several smaller branches; T1-DC present. H-VCT similar to H-DCT, arcing medially then anteriad toward head. T1-AWL branching dorsoventrally; T1-VC present, separating from T1-AL while remainder of T1-AL continues into foreleg. T2-AWL extending posteriad and slightly dorsad, bifurcating into T2-AL and T2-Wbr; T2-AL continues ventrad and posteriorly into midleg; T2-Wbr running dorsad and laterally, connecting directly with T2-S. T2-DB extending medially, ventrad and slightly anteriad, with three branches: T1-PL, T2-DLT, T2-VT. T1-PL extending through coxae before joining with T1-AL and continuing into proleg; T1-Fm visible. T2-DLT proceeds anteriorly to connect directly with T3-S via T3-DB. T2-VLT ventrad and posteriad, following mesothoracic sternite before arcing anteriad to link with T3-S. T3-S with four branches: T2-Wbr, T3-AWL, T3-DB, T3-VB. T2-Wbr extends from T2-S linking directly to T3-S. T3-AWL extending slightly dorsad before turning ventrad and laterally, bifurcating into T3-AL and T3-Wbr; T3-AL continues posteriorly into hindleg; T3-Wbr extending posteriad to connect directly to T3-S. T3-DB running mediad, linking with T2-DLT from anterior and T3-DLT continuing posteriorly. T3-VB runs mediad and posteriorly, with T3-VLT branching posteriad; T3-VB subsequently bifurcates into T2-PL and T2-VLT connection from T2-S. T2-PL runs anteriad from T3-S, joining with T2-AL from T2-S, continuing into midleg; several T2-Fm present. T3-VLT with T3-VL into hindleg femur. ABDOMEN: A1..8-S present. A1-S highly modified from subsequent segments, placed dorsally with four branches: T3-Wbr, A1-DB, A1-VB, T3-PL. T3-Wbr connecting directly from T3-S; small T3-Wbr-Vi extends dorsad and medially along metathoracic tergite. A1-DB mediad, linking with T3-DLT from anterior and A1-DLT continuing posteriad. A1-VB ventrad, with A1-VLT branching directly posteriad; A1-VB continues ventrally, bifurcating into T3-Fm, extending laterally into hind leg, and A1-VC; T3-VLT connects with A1-VC. T3-PL runs ventrad and posteriad, joining with T3-AL before extending into hindleg. Tracheae from A2..6-S similar, A4-S described here as example. A4-S with three branches: A3-VLT, A4-DB, and A4-VLT. A3-VLT runs anteriad, extending from A3-S. A4-VLT branches medially and dorsad before curving posteriad and laterally toward A5.S. At apex of this arc A4-VLT- Vi extends anteriorly, spanning several segments. A n -VLT-Vi variable, see taxon descriptions below. Midway between A4-S and A5-S, A4-VC branches ventrad at right angle, following abdominal sternite. A4-DB directly dorsad; A3-DLT connecting from anterior and A4-DLT from posterior to form Y-shaped junction. Visceral tracheae extend from either end of A4-DB: A4-DB-Mvi extends laterally and dorsad from start (ventral end) of A4-DB; A4-DB-Dvi from base of Y-shaped junction with A3-DLT and A4-DLT. A4-DLT-Dvi present but A4-DC absent. A n -DLT-Vi numerous and highly variable, see descriptions below. A7-S connections like previous segments but distance between A7-S and A8-S greatly shortened. A8-DB with three tracheae: A7-VLT, A8-DB, and A8-VLT, but with posterior branching varying between taxa, see descriptions below. Extensive tracheation in A7 and A 8 in both genera, no doubt for large muscles that control the forceps., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Westneat, M. W., et al. 2003. Tracheal respiration in insects visualized with synchrotron X-ray imaging. Science 299: 558 - 560.","Neubert, D., S. Simon, R. G. Beutel, and B. Wipfler. 2017. The head of the earwig Forficula auricularia (Dermaptera) and its evolutionary implications. Arthropod Systematics and Phylogeny 75 (1): 99 - 124.","Haas, F. 2018. Biodiversity of Dermaptera. In R. G. Footit and P. H. Adler (editors), Insect biodiversity: science and society: 315 - 334. Hoboken, NJ: John Wiley & Sons Ltd.","Wipfler, B., et al. 2020. Phylogenomics changes our understanding about earwig evolution. Systematic Entomology 45 (3): 516 - 526."]}

INFRAORDER ISOPTERA Although the respiratory physiology of termites (especially as it relates to their digestive system) has been studied for decades, micro-CT scans of respiratory architectures have been absent. The tracheal scans of the reproductive caste Reticulatermes flavipes and soldier caster Zootermopsis angusticollis shown here detail the remarkable intricacy of tracheal branches, especially in the abdomen, well known for its adaptations for digesting cellulose. Although both specimens were scanned at approximately 5 µm resolution, the worker Reticulitermes possesses notably smaller tracheae than the soldier Zootermopsis. Although the two specimens feature many similarities, notably a T1-DLT prothoracic “loop,” the differences are sufficient to describe both in detail. Wing-leg branching patterns, referred to here as Chapman’s Triangle (see Discussion section), are evident in both termites, albeit with some minor modifications (Chapman, 1918). In Zootermopsis, T2-AWL branches from T2-DB rather than directly from T2-S (as in Dermaptera and others), T3-AWL is off T3-S. In Reticulitermes, T2-VL branches from T2-VB, rather than T2-VLT, and T3-VL branches off T3-VB. (These could be Tn-Cx and not Tn-VL.), Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159, {"references":["Chapman, R. N. 1918. The basal connections of the tracheae of the wings of insects. In The Wings of insects: 27 - 51. Ithaca, NY: Cornell University Press."]}

Anisolabis maritima “Maritime earwig” Figures 44 (lateral), 45 (dorsal, ventral) Plates 24 (lateral), 25 (dorsal, ventral) A greater number of smaller tracheae are visible in the Anisolabis scan than the Forficula scan. As the CT scans for this study specifically targeted tracheal morphology, visualization of internal morphology of organs and internal structures was generally not possible. Therefore, determining the specific tissues supplied by a given trachea is challenging. However, some structures appear to have a particular tracheal morphology, such as muscle fibers and some other structures, and the detail afforded in the Anisolabis scan allows for some possibilities. For example, A 3-VLT-Vi begins by branching from A 3- VLT and proceeding anteriorly. Just before reaching the anterior end of the abdomen; however, A 3-VLT-Vi splits into several smaller tracheae that turn posteriorly to form a cone, most likely the tracheation of a portion of the alimentary canal, possibly the proventriculus. Additional detail is observable in the terminalia, specifically the cerci. As mentioned previously, extensive tracheation of A 7 and A 8 is for musculature controlling the forceps, and two tracheae are seen extending into the cerci. A 8-DLT-Cr is supplied by A 8- DLT, which arcs ventrad and posteriorly into each side of the forceps, and a second trachea A 8-VLT-Cr from A 8- VLT, reaching basically straight posteriad to cross over A 8-DLT-Cr into the cerci. DESCRIPTION: HEAD: H-DCT and H-VCT similar diameter; H-DCTs curve inward slightly such that left and right tracheae nearly touch before turning laterally outward on entry to head capsule; H-VCTs both proceed straight into head. H-DCT with several branches just anterior of cervix: H-DCC, H-DCT-Dvi, H-Oc, and H-Ant. H-DCC present, with several small H-DCC-Dvi fanning laterally and anteriad along head capsule. H-DCT-Dvi runs laterally and dorsad, branching off H-Oc. H-Oc arcing laterally, with several small tracheae extending into eye, then continuing anteriorly and ventrad via H-Oc-Md to link with ventral H-Md; H-Oc-Ant branches off H-Oc into antenna. H-Ant extends anteriorly through head into antenna; H-Ant with multiple tracheae in Anisolabis (H-Md-Ant, below). H-VCT likewise with several branches just anterior of cervix: H-VCT-Vi, H-Ft-Lbr, H-VC, and H-Mx-Md. H-VCT-Vi laterally and dorsad, like dorsal trachea. H-Ft-Lbr anteriad, with H-VC extending medially to link left and right sides; H-Ft branching laterally and anteriad with H-Lbr running directly anteriad. Both H-VC with H-VC-Dvi running directly anteriad. H-Ft-Lbr runs anteriad, with small H-Ft splitting laterally and anteriad, remaining H-Lbr running anteriad. H-Mx-Md runs anteriad and slightly laterally, with several branches: H-Lbm run ventrad, with short H-LbmPlp; H-Mx running ventrad, with short H-MxPlp. Remaining H-Md branch runs anteriad, with H-Oc-Md connection from H-DCT; H-Md-Ant branching dorsally to parallel H-Ant from H-DCT. THORAX: T 1-DVi branching from H-DCT closer to T 2- S than in Forficula. T 1-MVi visible. Several T 1-Fm visible. T 3-VL with connection to VLT near A 1-VB connection, forming X-shaped chiasma. ABDOMEN: A 4-DLT-Mvi branching from interior side of A 4- DLT, slightly posterior to junction with A 4-DB on right side of the body but nearly at Y-shaped junction on the left side. Branching of A n -DLT-Mvi from interior side of the dorsal longitudinal trunk varies between left and right side, but general anterior-posterior direction of tracheae is consistent for each segment (see fig. 46). A 4-VLT-Vi anteriad, extending through nearly two body segments. Anterior direction of A n - VLT-Vi consistent for Anisolabis. A 8-VLT-Cr and A 8-DLT-Cr extending into forceps., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159

Extatosoma tiaratum “Spiny leaf insect” Figures 85, 86 (lateral, anterior, posterior); 87, 88 (dorsal, anterior, posterior); 89, 90 (ventral, anterior, posterior) Plates 52 (lateral), 53 (dorsal), 54 (ventral) The spiny leaf insect Extatosoma tiaratum features a highly networked tracheal system with many lateral commissures and longitudinal connections. The posterior portion of the abdomen features a dense packing of noodlelike visceral tracheae that has morphological similarities to a package of dried ramen noodles, likely important for ventilation of the ovaries during the con- tinuous egg production of adult females. A n - DLT and A n - VLT are discernible in regions, along with larger anatomical features such as the location of spiracles, but the complexity of the specimen calls for a more in-depth analysis than can be presented here. Interested readers are encouraged to view the 3D models in the supplementary digital data., Published as part of Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, pp. 1-184 in Bulletin of the American Museum of Natural History 459 (1) on pages 1-184, DOI: 10.5531/sd.sp.55, http://zenodo.org/record/7730159