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Allometry is a common technique used by biologists to quantify and describe the exaggerated sexually selected traits of beetles. While horned species have dominated studies documenting weapon evolution among beetles, there is remarkable diversity in weapon type, including enormous mandibles, robust hind legs and elongated rostra. Here, I characterise intrasexual and intraspecific variation in body size, head size and shape in the anthribid weevil Hoherius meinertzhageni using traditional linear and 2D geometric morphometric approaches. Large males possess a broadened, shield-like head, which is much smaller in females and small-bodied males. Males were significantly larger in head and body size than females, and showed higher levels of variation in head and mandible size. Males exhibited an intrasexual dimorphism in head width and mandible length, but not head or antenna length. Overall, male head and mandible size showed hyperallometry, but minor males showed significantly steeper allometric slopes compared to major males and females. Geometric morphometrics revealed distinct differences in head shape between all groups (major and minor males, females). There were significant differences in the magnitude and direction of trajectories in size-shape space between males and females, with males showing more shape change per unit of size than females. In addition, there were significant differences in trajectory length but not slope angle between minor and major males. Overall, this combined approach using allometry with both traditional linear morphometrics and geometric morphometrics suggests that sexual selection is driving divergence in weapon size and shape among males and between the sexes. Preliminary behavioural observations support the hypothesis that weapon morphology corresponds to alternative mating tactics, although a more thorough investigation into the mating system of H. meinertzhageni is required.

Cimbicidae is a small family of Tenthredinoidea, containing the largest extant true sawflies. Body length variation across the family is mapped on an existing phylogeny, and some potential drivers of body size increase are explored: intrasexual competition between males, and mimicry patterns. Body length varies substantially within Cimbicidae, the largest species being found within the subfamily Cimbicinae. The smallest species occur in Corynidinae; this subfamily has experienced an overall decrease in body size. Initially, body size increase in Cimbicinae is correlated with males becoming larger than females, increase in relative mandible size in both sexes but especially in males, and increased hind femur width/length ratio in males only. Relative mandible size decreases in Cimbex spp. + Odontocimbex and hind femur width/length in male Leptocimbex spp., respectively. The record sizes obtained in Cimbex spp. + Odontocimbex are the result of a further increase in body size, coupled with increase in hind femur width/length ratio in males. Black and yellow body colouration and other potential mimicry patterns are observed in a number of genera of Cimbicinae, but are probably not ground plan features of the subfamily. Outside Cimbicinae, black and yellow body colouration is most frequent in Corynidinae, but it cannot be decided if it is a ground plan trait of this subfamily. Intrasexual competition seems to be more likely to have influenced size increase in Cimbicinae than adaptations to mimicry.

Two species of the calanoid copepod genus Bestiolina occurred in estuarine/coastal waters of the Nansei Islands, southernmost Japan. One of them is described herein as Bestiolina okinawae sp. nov., which is distinguished from known congeners by a combination of the following characteristics: 1) fifth pedigerous somite bearing groups of tiny spinules on the posterior end, 2) female mandible bearing a rod-shaped first gnathal tooth, 3) male left leg 5 with short apical spine on long terminal segment, and 4) legs 2–3 with endopodal segment 2 lacking spinules. The new species was the dominant zooplankter in oligohaline waters. The other species is morphologically identifiable to Bestiolina similis (Sewell, 1914). Genetic analysis using COI revealed that the two species differed by 9.9–10.0%, in contrast to small intra-specific genetic variation (0.0–1.5%). The two species were spatially segregated in low-salinity (2–30) estuaries and high-salinity (25–36) coastal waters, respectively, but co-occurred in some samples. Their body length decreased from the winter (around 20°C) to the summer (around 30°C) by 9.5–18.1%, depending on the species and sex. In both species, adult males, which lack mandibular gnathobase, were larger than the adult females.

Thrissina supra sp. nov. is described based on 15 specimens collected from Sindh, Pakistan. The new species is closely related to Thrissina whiteheadi (Wongratana 1983), which is herein redescribed, both species having a relatively long upper jaw with the posterior tip slightly beyond the opercle posterior margin, the snout tip above the eye center level, similar numbers of gill rakers, ventral scutes, and fin rays, and the first supramaxilla absent. However, the former is characterized by higher counts of longitudinal scale rows (45–47 vs. 40–42 in T. whiteheadi), transverse scales (12 or 13 vs. 10 or 11), total gill rakers on the first, second, third, and fourth gill arches [35–39, 33–37, 22–24, and 18–22, respectively vs. 30–34 (rarely 36), 29–32 (34), 19–21 (23), and 15–18 (14, 19), respectively], and branched anal-fin rays [42–45 (rarely 40) vs. 39–42 (43)], a longer snout (3.7–4.1% SL vs. 3.1–3.6%), pelvic fin (9.0–10.4% SL vs. 7.7–9.0%), and mandible (17.3–18.3% SL vs. 15.4–17.2%), a shorter pelvic-fin insertion to anal-fin origin distance (17.0–18.8% SL vs. 19.1–24.2%), and distinct paired dark lines along the dorsum from the occiput to the caudal-fin base (vs. uniformly distributed dorsal melanophores).

Cetoniinae is one of the showiest scarab groups, exhibiting bright-metallic body colors, and usually attract great attention from entomologists and amateur collectors. Larvae of Cetoniinae show dramatically diversity on morphology and living habits. Although being considered one of the best-studied groups of Scarabaeidae, larvae have been described for less than 5% species to the known Cetoniinae. In this study, the final instar larva of Lasiotrichius succinctus hananoi was described using scanning electron microscopy. The larvae are peculiar for bearing a haptomeral process dividing 10 spines into two groups: six on the left side, four on the right side, different from the previous descriptions on L. succinctus (Pallas, 1781). The morphological differences under SEM imply the further requirement of taxonomic revision in Lasiotrichius. Both advantage and disadvantage of SEM utilizing in larval descriptions were briefly discussed.

Genetic sequencing (with mtCOI) was used to associate larvae with two new Vietnamese caddisfly (Trichoptera) species from Bach Mã National Park, Hydromanicus calyx n. sp. (Hydropsychidae) and Drepanocentron dentatum n. sp. (Xiphocentronidae). Adult Drepanocentron dentatum n. sp. is distinguishable by the toothy dorsal margin of the male inferior appendages; the most similar species, D. vercaius, has teeth on the ventral, but not the dorsal margins of the inferior appendages. The larva of D. dentatum is fully described herein, the first larva to be described in the genus Drepanocentron; it can be separated from the other two known xiphocentronid larvae (Xiphocentron messapus and Cnodocentron yavapai) by the smooth, thin mesal margin of each mandible. Adult Hydromanicus calyx n. sp. is distinguishable by the cupped apices of the male harpagones; this character is absent in morphologically similar species (H. nieuwenhuisi, H. abiud, and H. serubabel). The larva of H. calyx is morphologically most similar to that of H. inferior, but can be distinguished by the presence of faint muscle scars interrupting the lateral margins of the stridulatory areas on the venter of the head.

Halocyprid ostracods are appreciable part of ostracods floating through virtually everywhere in marine environment. In this study, we describe a new species of genus Polyconchoecia Xiang, Chen and Du, 2018, tribe Conchoeciini Chavtur and Angel, 2011, family Halocyprididae Dana, 1853 from the middle of the South China Sea. Polyconchoecia chenii sp. nov. is very close to P. commixtus Xiang, Chen and Du, 2018. But it differs from P. commixtus by the distinctions of locations of major glands of carapace and the characteristics of appendages: more posteriorly situated left asymmetric gland of carapace, no right asymmetric gland; segmented frontal organ; the endopod 2 of the first antenna with a very small seta; a- and c-setae of the first antenna with long end joint have long end joint, the b- and d-setae have no end joint, spinose e-seta without end joint; the e-seta of the second antenna is present; teeth side is distinctive; the setal counts of the mandible, maxilla, fifth limb, and sixth limb are individual. The locations of the major glands on carapace and the characteristics of the first antenna can be the key of the new species. This work is the second discovery of the genus Polyconchoecia from the world.

Dussumieria torpedo, new species, is described from 18 specimens collected off the East African coast from Tanzania to South Africa. The new species closely resembles Dussumieria albulina in that both species have a deep body and a parasphenoid without teeth. However, D. torpedo, new species, is distinguished from D. albulina by having small pores posteriorly on the body scales (vs. numerous longitudinal striae posteriorly in D. albulina), a longer maxilla (33.4–34.9% of head length vs. 30.4–34.9% [less than 33.3% in specimens larger than 85 mm standard length]) and mandible (48.5–51.9% of head length vs. 44.8–50.6%), a greater number of pseudobranchial filaments (19–23 vs. 17–21), and indistinct melanophores scattered on the pectoral-fin rays (vs. distinct). A molecular analysis, which compared nucleotide sequences of the mitochondrial cytochrome oxidase I (COI) gene of the new species with those of all other valid species of Dussumieria, revealed that D. torpedo, new species, has >9% mean p-distance divergence from its congeners.

For the first time the role of rhyncholites in the process of epibiota has been figured out. Serpulidae inlay is detected in 39 rhyncholites of 979 specimens, representing 4% of the all studied material. This fact demonstrates that rhyncholites were used extremely rarely by encrusting species as a substrate. No other epibionts were found. Polychaetes were found in the genus Hadrocheilus (87%) and in the genus Akidocheilus. Size of the inlaid rhyncholites ranges from 7 to 23 mm. Serpulidae cover usually only the ventral side of rhyncholites, herewith, at 48,7% of the samples epibionts with different degrees of intensity are developed throughout the ventral surface, at 30,7% of the samples they are observed only on the ventral side of the hood and at 20,6% serpulidae are present only on the ventral surface of the arm. At four exemplars of the genus Hadrocheilus (10 % of the total amount) polychaetes are developed on the dorsal surface, but they are always and usually very wide developed on the ventral side of rhyncholites. No samples were found in which serpulidae were found only on the dorsal surface. Among the remains of polychaete worms, large and small tubes were identified and described. The presence of serpulidae on the handle of rhyncholites, that during the life of the cephalopod mollusk was located in a horny jaw, is a clear indication of the settlement’s epibionts on isolated skeletal structures of the already dead cephalopod. Cases when serpulidae are observed only on the ventral side of the hood in representatives of the genus Akidocheilus, suggest that planktonic trochophore – larvae of polychaetes can settle on the inner surface of the mandible of living ammonoids, where they turned into an adult worm. At the same time, polychaetes gained access not only to traditional prey, represented by various microscopic organisms, but also to additional food resources associated with the life activity of cephalopodas.

Male Aegus chelifer chelifer stag beetles are normally equipped with long mandibles as a weapon to compete with rival males over females, where fighting or aggressive behavior is generally expected during the encounter between two male stag beetles. However, three main patterns were observed between 164 pairings of male stag beetles. Besides the predominant aggressive or fighting behavior (107 pairings), male stag beetles also exhibited disregarding behavior (29 pairings) and same-sex sexual behavior (28 pairings). For sexual interactions, active males exhibited courting and mating behavior as found in male-female interactions, but the insemination process was unsuccessful. Responses of passive males varied from totally passive to resisting and running away. Visual confusion of short-mandible males for females by active males was not likely to be responsible for the same-sex sexual behavior because the correlation between body size and the sexual behavior or sexual role between male-male pairs was not significant. Rather, sexual recognition via chemicals on the cuticle surface might be responsible for the same-sex sexual behavior.

We describe a new extinct spiny rat,Proclinodontomys dondasin. gen. n. sp. (Rodentia, Caviomorpha, Echimyidae), represented by a noteworthy preserved skull and mandible from the early-middle Pleistocene outcrops at the coastal cliffs of SE Buenos Aires Province (Central Argentina). Phylogenetic analyses allow us to propose that the new species described here and the already knownEurzygomatomys mordax(Winge) represent a new genus closely related to the livingEuryzygomatomys spinosusandClyomys laticeps. The new genus differs fromEuryzygomatomysandClyomysby having much more procumbent upper incisors, a more developed fossa for the M. temporalis, more flared and laterally expanded zygomatic arches, frontal less markedly expanded posteriorly, jugals much deeper anteriorly than posteriorly, with the dorsal border descending more abruptly posteriorly, smaller orbital cavity, and external auditory meatus relatively smaller and slanted upward and backward. Several features of the new species reflect a higher degree of adaptation to semifossorial habits than those ofE.spinosus. The origin of the semifossorial ecomorphotype within echimyids may have been triggered by the expansion of relatively open and arid environments that arose near the Miocene-Pliocene boundary. The record of this new echimyid in Central Argentina indicates that during the early-middle Pleistocene, the southern limit of the geographic range of extinct representatives of the Brazilian lineage of semifossorial echimyids extended farther south than that of their living members.UUID:http://zoobank.org/c30ec1fe-4352-4867-a02f-e0d45c884bfe

Male insects with large weapons such as horns and elongate mandibles would be expected to invest more on such structures than other parts of the body for advantages in male to male competition for mating. In male genitalia, however, intermediate size provides a better fit for more females than small or large sizes, and such a male would leave more offspring regardless of their body size. These predictions were tested using a static allometry analysis between body size and other trait sizes. Acanthacorydalisasiatica is a large dobsonfly (Megalotera) and males have conspicuously large mandibles used as weapons. We examined the hypothesis that the male mandibles of this sexually dimorphic species are sexually selected to enlarge, whereas the male genitalia are stable to be intermediate regardless of a great variation in body size. The results, as predicted, showed positive allometry between male body size and mandible length but negative allometry between male body size and ectoproct length (a male grasping structure). Sperm are transferred through a small spermatophore attached externally to the female genital opening, so it may be evolutionarily unnecessary to develop an enlarged male genital size. In contrast, there may be a trade-off between male mandible size and wing length, because of negative allometry between body size and wing length in males but isometry between them in females.

International audience; The house mouse (Mus musculus domesticus), as a successful invasive species worldwide, has to forage a variety of resources. Subantarctic mice display among the most notable diet shift from the usual omnivorous–granivorous diet, relying on a larger proportion of terrestrial animal prey. In agreement, a recent study of their mandible morphology evidenced an evolution of their mandible shape to optimize incisor biting and hence seize preys. Here, the incisors themselves are the focus of a morphometric analysis combined with a 3D study of their internal structure, aiming at a comparison between subantarctic populations (Guillou island, Kerguelen archipelago) with a range of western European continental, commensal mice. The predatory foraging behavior of Guillou mice was indeed associated with a sharper bevel of the lower incisor, which appears as an efficient morphology for piercing prey. The incisor of these mice also displays a reduced pulp cavity, suggesting slower eruption counterbalancing a reduced abrasion on such soft food material. The dynamics of the ever‐growing incisor may thus allow adaptive incisor sculpting and participate to the success of mice in foraging diverse resources

Adult horned beetles (Coleoptera, Scarabaeidae, Dynastinae) such as Trypoxylusdichotomus (Linnaeus, 1771) exhibit bark-carving behaviors to feed on tree sap, in part by using small projections of the clypeus. However, in the present experiments, adult horned beetles (T.dichotomus and Dynasteshercules (Linnaeus, 1758)) used their mandibles and not the projections of the clypeus to carve bark. Our findings show the presence of completely engaged mandibular interlocking, gear-like surface structures in molar areas that guide mandible opening and closure, and lead to completely synchronous movements of adult horned beetle mandibles. Three-dimensional shapes of these mandibular gear-like structures are complex and remained in contact after the death of a beetle. Moreover, adult horned beetles often performed bark-carving behaviors using only the mandible of one side, suggesting that the primary role of the mandibular gear-like structure is to prevent breakage of the mandible by transmitting load from one mandible to the other. Among the 22 Dynastinae and 16 other beetle species examined (not Dynastinae), the gear-like structure was found in all the Dynastinae species and in no other species.

El objetivo fue analizar si el consumo de diferentes plantas influenciaba el tamaño/forma de las mandíbulas de larvas de lepidópteros oligófagas y si dicho consumo ocasionaba tasas de crecimiento diferenciadas entre el músculo aductor mandibular y las mandíbulas durante su ontogénesis. Para esto se usaron larvas de Heliconius erato criadas en cuatro plantas hospederas naturales, a las que se les tomaron medidas de longitud de cápsula cefálica, tamaño mandibular y área del músculo aductor. Para detectar eventuales diferencias de forma mandibular se empleó microscopía electrónica y morfometria geométrica, y para posibles cambios alométricos se realizaron comparaciones entre curvas de crecimiento mandíbula vs. músculo aductor de los individuos criados en las cuatro plantas hospederas. Se encontró que no existen diferencias de tamaño entre las mandíbulas ni en músculos aductores de individuos criados en las diferentes plantas pero la forma mandibular fue significativamente diferente, mostrando una relación directa con la planta hospedera usada como alimento. Generalmente, la mandíbula creció proporcionalmente más que el músculo aductor, cuyo crecimiento fue estable. El cambio más significativo fue el alargamiento de los dientes incisivos en mandíbulas de larvas criadas con Passiflora suberosa. Se sugiere que esto se debe a que las hojas de esta especie poseen mayor dureza comparadas con las otras y que el desarrollar dientes largos facilitaría su corte y consumo.

The morphology of the skull contains considerable ecological information about a species, because the skull contains sensory organs that are used to look for food, compete for mates, or to migrate. Spotted seals (Phoca largha) and harbor seals (Phoca vitulina) are similar in body size and pelage color but differ in habitat use and reproductive biology. The current study aims to clarify differences in the shapes of skulls in the spotted and harbor seals using geometric morphometrics and to discuss whether ecological differences can explain morphological differences in skulls. First, we discovered that the age at which the shape of skulls stopped changing was 7 years in both species, using the linear-threshold model. Using a total of 75 landmarks, 54 individuals (25 spotted seals, 29 harbor seals) that were older than the age at which skulls stopped changing were correctly identified at a rate of 100%. The total of 75 landmarks was narrowed down to eight key landmarks that resulted in an identification accuracy rate of 100% using random forests. Of the eight landmarks, seven were related to feeding apparatus, indicated that the harbor seal had a broader mouth and mandible than the spotted seal. Because of both species were dietary generalists and classified as pierce feeders, we suggested that the different features in the shapes of their skulls were caused not only by differences in their feeding behavior but also other differences related to reproductive behavior.

Bill deformities have been documented in many avian species across the globe and can be caused by environmental or genetic conditions that may also reflect ecosystem health. We describe the first case of bill deformity in the genus Tyrannus, in a young male Western Kingbird (Tyrannus verticalis) that fledged from a nest in an industrial park in Memphis, Tennessee, USA. The upper mandible of the bill was curved to the left and below the plane of the normal lower mandible making it unlikely that the individual would be able to forage normally and survive to adulthood. Genetic testing for evidence of hybridization with Scissor-tailed Flycatchers (T. forficatus) showed no sign of introgression, and it is unclear what caused the deformity.

South American cervids have a relatively recent evolutionary history in the Neotropics. Present taxonomical richness includes six genera and 17 species grouped in at least two clades, Blastocerina and Odocoileina. With few exceptions, functional morphology or ecomorphological approaches have not been rigorously applied to the masticatory apparatus of Neotropical deer. In order to understand the relationship between craniomandibular integration and feeding behavior, we used geometric morphometric methods (3D landmarks) to quantify the strength and significance of the correlation between morphology and feeding behavior. Two blocks Partial Least Squares analyses, angular comparison, regression analysis, and independent contrast were performed to explore the patterns of covariation between cranial and mandibular shape and size, and between them and continuous dietary characters. The main variation in shape is related to a gradient from a brachycephalic cranium with a robust mandible in small deer to a dolicocephalic cranium with a gracile mandible in large deer. These shape changes seem to be modeled by a complex interplay of allometric trends and biomechanically significant features related to the proportions of dietary monocotyledon, fruit, or dicotyledonous plant material. We find remarkable convergences in the brocket deer ecomorphotype in the two clades of Neotropical cervids, as well as similar craniomandibular traits between marsh and pampas deer with African mixed feeder bovids related to monocotyledon consumption. These findings lead us to share Radinsky’s interest in convergences in the masticatory apparatus of herbivorous mammals. Fil: Cassini, Guillermo Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad Nacional de Luján; Argentina Fil: Toledo, Néstor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina

Aquatic predatory insects, like the nymphs of a dragonfly, use rapid movements to catch their prey and it presents challenges in terms of movements due to drag forces. Dragonfly nymphs are known to be voracious predators with structures and movements that are yet to be fully understood. Thus, we examine two main mouthparts of the dragonfly nymph (Libellulidae: Insecta: Odonata) that are used in prey capturing and cutting the prey. To observe and analyze the preying mechanism under water, we used high-speed photography and, electron microscopy. The morphological details suggest that the prey-capturing labium is a complex grasping mechanism with additional sensory organs that serve some functionality. The time taken for the protraction and retraction of labium during prey capture was estimated to be 187 &plusmn, 54 ms, suggesting that these nymphs have a rapid prey mechanism. The Young&rsquo, s modulus and hardness of the mandibles were estimated to be 9.1 &plusmn, 1.9 GPa and 0.85 &plusmn, 0.13 GPa, respectively. Such mechanical properties of the mandibles make them hard tools that can cut into the exoskeleton of the prey and also resistant to wear. Thus, studying such mechanisms with their sensory capabilities provides a unique opportunity to design and develop bioinspired underwater deployable mechanisms.

A new mayfly species, Sparsorythus sivaramakrishnani sp. nov. from the stream of Pullian cholai, Thuraiyur, Namakkal district, Tamil Nadu, India is described based on male and female nymphs. Sparsorythus sivaramakrishnani sp. nov. differs from the closely related S. gracilis by the shape of the left prostheca, the number of bristle-like processes at base of left prostheca, the ratio and shape of right prostheca, the ratio of femur length: width, the size of the female nymph, the mesonotum overlapping in fifth abdominal segment of the female, and by the shape of hypopharyngeal lingua.

Investigations of type material and new material from the Philippines (Luzon) revealed that Baetis luzonensis Müller-Liebenau, 1982 and B. realonae Müller-Liebenau, 1982 do not belong to Baetis Leach, 1815. A new genus, Philibaetisgen. nov., is described to accommodate both species and both are re-described based on larvae. The new genus is characterised by having a rectangular labrum with a submarginal row of long, simple setae on the dorsal surface and ventrally on lateral margins long, simple, spine-like setae, on anterolateral margins long, feathered setae and medially long, bifid setae and a partial, submarginal row of lanceolate setae. Both mandibles have blade-like incisors and dorsally, a mediolateral patch of long, spine-like setae; additionally, the left mandible has a tuft of long, partly branched setae at the base of the subtriangular process. Philibaetisgen. nov. is further characterised by a hypopharynx with a medial tuft of stout setae and anterolaterally, two smaller tufts of stout setae, a galea-lacinia with the distal denti-seta tooth-like and directed against canines, a fore femur apically with stout setae, both on anterior and posterior side and without a femoral patch and a claw with one row of denticles and two or three subapical setae. The protogonostyli under the cuticle of male last instar larvae are folded in the Labiobaetis type, excluding their affiliation to the genus Baetis. COI sequences were obtained from both species. The genetic distance (Kimura 2-parameter) between them is 17.5% on average. Very limited genetic distances of 0% to 3% (0.75% on average) were found between specimens of P. luzonensiscomb. nov.

The ant Harpegnathos venator can engage in various labors using a pair of elongated mandibles with the ability to rotate about two orthogonal axes. This biaxial rotation enables the ant to gently handle their small, fragile eggs with enhanced contact area and smaller work space. However, how this biaxial rotation influences the ant's predation ability and how the ant responds to this influence remain elusive. We quantitatively investigate the tribological performance of the ant's mandibles during interactions with prey by taking morphology and kinematics into consideration. We find that each ant mandible features unique, double-rows of dorsal and ventral teeth, which are employed to firmly clamp prey over a wide range of sizes by biting their different body parts, demonstrating the ant's predation ability. We hypothesize the mechanism underlying such an ability may rely on the two, non-parallel rows of teeth which potentially eliminate effects of biaxial rotation. To test this hypothesis, we systematically change the distribution and orientation of teeth on bio-inspired robotic mandibles and investigate the mandible tribological performance of different teeth configurations. We find that the friction coefficient varies prominently between the dorsal and ventral teeth resulting from biaxial rotation, with the variations showing an inverse pattern. This explains the observed phenomenon that mandibles equipped with dorsal and ventral teeth provide the most stable friction coefficient when clamping objects of different sizes using different mandible regions. The specialized distribution of teeth facilitates enhanced tribological stability in capturing prey, and demonstrates an intrinsic link between the form, motion, and function in the insect appendages. Our research sheds lights on the current understanding of the predation behaviors of ants, and can inspire future design of multifunctional robotic grippers.

Ambrosia beetles from the genus Xyleborus are important vectors of fungal pathogens in forest and agricultural systems, yet the influence of temperature on their morphological development has been poorly studied. Because host colonization and ambrosial fungi cultivation is mostly restricted to females, it is possible to speculate on strong sexual dimorphism expression in secondary sexual characters and ecological segregation between sexes. Here, we determined the effect of different growing temperatures (17, 23, 26 and 29 °C) on mandible ontogeny of larvae and adult individuals of X. affinis, and sexual dimorphism in adults, in shape and size variation using geometric morphometrics. Mandible shape change showed significant differences in magnitude and direction through larval ontogeny among temperature treatments. Sexual shape and size dimorphism were found in adult mandibles, and the degree of sexual dimorphism was dependent on growth temperature, with a significant effect of the interaction between temperature and sex on mandible shape and size variation. Higher morphological differences were observed at the base of mandibles among temperature treatments in adults and a gradual narrowing trend with temperature increments. These findings could have consequences on feeding performance and fungus cultivation inside colonies, potentially influencing their ability to establish populations in new geographical areas.

This paper describes the previously unknown larva of Plectrocnemia scruposa McLachlan 1880. Information on the morphology of the 5th larval instar is given, and the most important diagnostic features are illustrated. In the context of existing identification keys, P. scruposa keys together with P. brevis McLachlan 1871, P. conspersa (Curtis 1834), and P. laetabilis McLachlan 1880. These species can be separated by the length of the outermost seta of the posterolateral trio on the last abdominal tergum and by presence/absence of a central pigmented mark on the posterior margin of the labrum. According to mandible morphology, the larva of this species appears to be mainly a predator and passive filter feeder of particulate organic matter.

Wood boring is a feature of several insect species and is a major cause of severe and irreparable damage to trees. Adult females typically deposit their eggs on the stem surface under bark scales. The emerging hatchlings live within wood during their larval phase, avoiding possible predation, whilst continually boring and tunneling through wood until pupation. A study of wood boring by insects offers unique insights into the bioengineering principles that drive evolutionary adaptations. We show that larval mandibles of the coffee wood stem borer beetle (Xylotrechus quadripes: Cerambycidae) have a highly sharp cusp edge to initiate fractures in Arabica wood and a suitable shape to generate small wood chips that are suitable for digestion. Cuticle hardness at the tip is significantly enhanced through zinc-enrichment. A hollow architecture significantly reduces bending stresses at the mandibular base without compromising the structural integrity. Finite element model of the mandible showed highest stresses in the tip region; these decreased to significantly lower values at the start of the hollow section. A scaling model based on a fracture mechanics framework shows the importance of the mandible shape in generating optimal chip sizes. These findings contain general principles in tool design and put in focus interactions of insects and their woody hosts.

The mature larva ofCionus olivieriRosenschoeld, 1838 is described and illustrated in detail for the first time. It is compared with those known from the same genus and other genera in the tribe Cionini and with those of the hypothesized sister tribe Mecinini in the Curculioninae. The larvae ofCionushave three distinctive diagnostic features: the reduced number of setae on the epicranium (only two or threedesand one or twofs) and on the epipharyngeal lining (only twoals, twoams, and nomes); i.e., distinctly fewer than the most frequent number of setae in weevils, and mandibles dentate or angulate internally near the base. If considered together withStereonychusSuffrian, 1854, the other genus of Cionini with larvae studied in detail, it is preliminarily suggested that mature larvae of this tribe might be characterized by six main diagnostic features: (1) labial palpi one-segmented, (2) labral rods absent, (3) pedal areas swollen to form large lobes or prolegs, (4) mandible with sharp apical teeth, (5) reduced number offson frons, only one or twofs, and (6) reduced number of epipharyngeal setae (two or threealsand two or threeams, but nomes). It was noticed thatC. helleriReitter, 1904 from Japan, a very distinct species in the genus for some characters of the adult, also possesses distinctive characters in the larva which are uncommon among known cionines. New biological data onC. olivieriwith the discovery of its host plant,Verbascum songaricum(Scrophulariaceae), in central Asia are also reported.

Background In species with parental care, there is striking variation in offspring dependence at birth, ranging from feeding independence to complete dependency on parents for nutrition. Frequently, highly dependent offspring further evolve reductions or alterations of morphological traits that would otherwise promote self‐sufficiency. Here, we examine evidence for morphological evolution associated with dependence in burying beetles (Nicrophorus spp.), in which dependence upon parents appears to have several independent origins. In many species, precocial first instar larvae can survive without parenting, but several altricial species die at this stage on their own. We focused specifically on the mandibles, which are expected to be related to feeding ability and therefore independence from parents. Results We find no evidence that the size of the mandible is related to dependence on parents. However, we do find a developmental and phylogenetic correlation between independence and the presence of serrations on the inner edge of the mandible. Mandibles of independent species bear serrations at hatching, whereas dependent species hatch with smooth mandibles, only developing serrations in the second instar when these larvae gain the ability to survive on their own. Phylogenetic evidence suggests that serrations coincide with independence repeatedly. We note a single exception to this trend, a beetle with a serrated mandible that cannot survive without parents. However, this exception occurs in a species that has recently evolved the loss of independence. Conclusions We argue that the absence of mandible serrations occurs due to alternative selection pressures incurred in larvae dependent upon parents to survive. We suggest that this may have led to a variable function for mandibles, perhaps related to increased competitive ability among siblings or increased efficiency in receiving nutrition from parents. Furthermore, we propose that the phylogenetic pattern we see is consistent with the long‐held evolutionary hypothesis that evolutionary change in behavior and physiology precede morphological change.

Two new species of aquatic acentropines, Petrophila anna, new species, and Petrophila cornvillia, new species, are described and illustrated from northcentral Arizona, U.S.A. Both species were initially found in Oak Creek which traverses both Coconino and Yavapai counties, but were observed most frequently at and below Red Rock Crossing in Coconino County where the creek flows southwest to the Verde River. Observations regarding adult flight period, a unique cocoon texture created by sand, and larval mandible morphology are summarized. A table comparing the genitalic differences between the two new species and three externally similar species of Petrophila is provided.

Radiotransmitters have been used successfully to track and recapture giant wētā (Deinacrida species) in part to assess mating success. We report the successful use of very light transmitters (0.2 g) to track male Wellington tree wētā, Hemideina crassidens, over several nights to daytime refuges in burrows and tree galleries. Male Hemideina species sport lengthy mandibles used as weapons in fights with rivals over groups of females living in gallery refuges. Consistent with previous studies showing that males with the longest mandibles cohabit with the largest groups of females, our two largest radio-tagged males were the only ones relocated with adult females.

We describe and illustrate for the first time the third-instar larvae of three Anastrepha species, Anastrepha pickeli Lima, Anastrepha pulchra Stone, and Anastrepha curitis Stone, and also the second instar of A. curitis. Structures such as the cephalopharyngeal skeleton and spiracles are described using optical and scanning electron microscopy. We describe characteristics of the ventral surface of the mandible for the first time for fruit fly larvae.

Araecerus is genus of beetles of the Anthribidae family which are important economic pests of various crops including coffee (Rubiaceae), with A.fasciculatus (Degeer) being the common pest (weevil) of coffee beans. This paper presents a study in which five undescribed species of genus Araecerus were reared predominantly from the seeds of M.pachyclados (Rubiceae), a native tree of Papua New Guinea (PNG). Fruits of M. pachyclados were regularly sampled and insects attacking them were reared, preserved and identified. Fruits were hand collected, photographed, weighed and reared. Insects emerging from the fruits were captured and preserved in 99% ethanol. All the specimens were identified into morphospecies at the laboratory. The five new species discovered were designated as A. sp.1, A. sp.2, A. sp.3, A. sp.4 and A.sp.5. This was accorded based on differences in body length; scutellum color, size, hair-scales and visibility; length of first and second segments of fore tarsus; apical and subapical teeth-size (mandible and maxillary palpi); declivity of dorsal abdomen; basal-anterior eye markings; lateral eye markings; absence of eye markings; and shape of pygidium. We discovered A. sp.1 has yellowish gold marking inside the base of the eye, A. sp.2 with pygidium almost vertically-flat at abdominal apex, A. sp.3 has eyes without yellowish gold marking and generally dark in color, A. sp.4 with distinct yellowish gold interior-lateral marking in its eye, and A. sp.5 with pygidium pointed at abdominal apex.

Myrmecophilus crickets are well-known inquilines that live and obtain food resources in ant nests. In Japanese Myrmecophilus species various degrees of host specificity are reflected in behavioral differences among species. For example, extremely specialized species perform trophallaxis with their host ant species, whereas generalist species may steal food from their hosts without any intimate contact. We examined behavioral variations among four Myrmecophilus species that use different hosts and show different degrees of specificity, and we also compared morphological traits such as mandible shape and hind leg length among the species. The morphometric analyses showed that an extreme host-specialist species had less complex and largely non-functional mandibles, reflecting its dependence on trophallaxis with its host ant species. In contrast, extreme host-generalist and/or moderate specialist species, which directly eat solid foods, had more complex and functional mandibles which they use to cut and crush their foods, such as insect carcasses and ant larvae. The extreme host-specialist species had shorter hind legs than the extreme host-generalist. This may reflect that it suffers few attacks from the host ants. Our results show that in Myrmecophilus food sources shape behavioral interactions with host ant species and correlate with morphological characteristics.

Many insects, including stag beetles, possess exaggerated structures and these structures usually grow disproportionately with their body size. Allometry, i.e. the scaling relationship between such traits and other body parts (used as proxies of body size in a species), can provide valuable information about development and evolution. We examined males of Aegus chelifer chelifer , a stag beetle from forest and urban habitats in Thailand to clarify the allometric relationship between weapon (mandible) and body (elytra) size. The relationship between the log-transformed mandible and elytra length was non-linear and best fitted the piecewise linear model. Moreover, this model revealed the existence of dimorphism in males that could be divided into minor and major morphs based on their mandible size, in broad agreement with the morph classification based on mandible shape. Both morphs from the two populations (urban and forest) exhibited positive allometry, and the allometric slope declined in the major morph. Comparison between populations showed the allometric slopes were similar, but the intercepts were significantly different in the major morphs. The genetic or environmental basis should be further explored for the two morphs as well as any behavioural variation.

In this paper, we describe the skulls of Magnificent Frigatebird Fregata magnificens (Fregatidae) and Brown Booby (Sulidae) Sula leucogaster, with focus on the structures associated with the Musculi mandibulae. We discuss the results in the context of the feeding biology of the two species, which feed mainly on flying fish and squids. Frigatebirds capture prey from just above, or just below, the water surface in flight. The hook-shaped Apex maxillae in F. magnificens can be viewed as an adaptation for grasping prey from near the water surface. Boobies catch prey by plunging; thus, the dorsoventrally flattened skull and conical bill of S. leucogaster may reduce water resistance when it dives, or swims underwater. The bill is long in both species, such that it is on average 70% of the whole skull length in F. magnificens and 60% in S. leucogaster. Consequently, the Mm. mandibulae in the two species are more posteriorly positioned relative to the Apex rostri. This results in low mechanical advantage for the mandible opening-closing lever, indicating adaptations for a fast, rather than a strong, bite. Fast-moving mandibles would be advantageous for ‘mandibulating’ prey while swallowing. The Fossa musculorum temporalium and the Palatum osseum in both species provide a broad area for origins of the Musculus adductor mandibulae externus (all parts) and the Musculus pterygoideus. The Processus orbitalis quadrati is longer and thicker in F. magnificens than in S. leucogaster, and so is the Musculus pseudotemporalis profundus. We suggest that Mm. adductores mandibulae are relatively well developed in the two species; therefore, their mandibulae are still probably capable of a powerful adduction. In both species there is a mechanisms that contribute to protect the jaws from disarticulation and damage. Such mechanism involves the incorporation of a ‘flange-like’ Crista intercotylare on the Margo medialis cotylae medialis fossae articularis quadratica that grips the Condylus medialis quadrati. In S. leucogaster, the retractor-stop ‘notch’ formed by Ossa lacrimale et nasale also serves to protect the jaws against sudden external forces when birds are diving or swimming underwater for prey. A more detailed hypothesis for the jaw movements and strength in F. magnificens and in S. leucogaster and their relation with feeding habits should necessarily incorporate data on the jaw and anterior neck musculatures.

"Se describen el primer y último estadios larvales y la pupa de Enagria ovata (Boheman, 1854). Al comparar el primer y último estadios de E. ovata con los de Asteriza flavicornis(Olivier, 1790),Cistudinella obducta (Boheman, 1854) y Physonota alutaceaBoheman, 1854,se encontraron diferencias morfológicas en el número de tubérculos laterales (escolos), de artejos en el palpo labial y dientes en la mandíbula. La pupa es distinta a la de A. flavicornis, por la ausencia de 2 proyecciones en el pronoto. La actividad de E. ovata inicia a finales de mayo y termina a principios de noviembre. Las hembras ovipositan entre 25 y 35 huevos, las larvas eclosionan en un periodo de 9-10 días y pasan por 6 estadios larvales en un periodo de 22 días. Las larvas y los adultos fueron observados alimentándose de Montanoa tomentosa Cervant (Asteraceae)."

The forests of the northern Rocky Mountains are hosts of nine species of Nearctic conifer-infesting bark beetles of the genus Scolytus Geoffroy. One of these, Scolytus piceae Swaine (Coleoptera: Curculionidae), infests spruces across the continent including Picea engelmannii Parry (Pinaceae) in Idaho. Mature larvae overwintered before transforming to adults, which infested new hosts in early June. Scolytus piceae most commonly infested shaded out lower branches of mature live spruce. In sporadic wind-felled spruce, the beetle infested the terminal portion of branches throughout the crown, whereas another Scolytinae, Polygraphus rufipennis (Kirby), infested the thicker bark basal portion of the same branches. This niche separation resulted from difference in time of their dispersal flight and ability of S. piceae to colonize thin bark by engraving the underlying sapwood. Population recruitment of S. piceae was low in shaded out lower branches, in balance with this limited host resource. Features of the head of S. piceae larvae differed from that reported in literature, including the mandible dentition, antennal field, and pattern of setae on the postlabium.

Several male beetles that fight with rival males show dimorphic weapons. Major males have large weapons and fight aggressively with rival males. Minor males have small or no weapons and often adopt an alternative reproductive tactic without fighting. Suitable body shapes are likely to differ depending on the tactic. Thus, the set of body parts that are compatible with distinct weapons may be different in major and minor males according to their battle tactics. Many studies have reported correlations between weapons and some morphological traits, but few studies have shown the difference in the correlation patterns between major and minor males. Here, we show that in a male dimorphic stag beetle, Prosopocoilus inclinatus (Motschlsky), several morph-specific traits are correlated with weapon size. Mandible size correlates positively with eye size in major males only but correlates positively with the length of forelegs and negatively with abdomen weight in minor males only. These results suggest that the correlated trait sets are different between the morphs because each morph adopts different battle tactics and mating strategies.

One of the defining features of the evolutionary success of insects is the morphological diversification of their appendages, especially mouthparts. Although most insects share a common mouthpart ground plan, there is remarkable diversity in the relative size and shapes of these appendages among different insect lineages. One of the most prominent examples of mouthpart modification can be found in the enlargement of mandibles in stag beetles (Coleoptera, Insecta). In order to understand the proximate mechanisms of mouthpart modification, we investigated the function of appendage-patterning genes in mandibular enlargement during extreme growth of the sexually dimorphic mandibles of the stag beetle Cyclommatus metallifer. Based on knowledge from Drosophila and Tribolium studies, we focused on seven appendage patterning genes (Distal-less (Dll), aristaless (al), dachshund (dac), homothorax (hth), Epidermal growth factor receptor (Egfr), escargot (esg), and Keren (Krn). In order to characterize the developmental function of these genes, we performed functional analyses by using RNA interference (RNAi). Importantly, we found that RNAi knockdown of dac resulted in a significant mandible size reduction in males but not in female mandibles. In addition to reducing the size of mandibles, dac knockdown also resulted in a loss of the serrate teeth structures on the mandibles of males and females. We found that al and hth play a significant role during morphogenesis of the large male-specific inner mandibular tooth. On the other hand, knockdown of the distal selector gene Dll did not affect mandible development, supporting the hypothesis that mandibles likely do not contain the distal-most region of the ancestral appendage and therefore co-option of Dll expression is unlikely to be involved in mandible enlargement in stag beetles. In addition to mandible development, we explored possible roles of these genes in controlling the divergent antennal morphology of Coleoptera.

The distribution, seasonality and reproductive characteristics of Carabus ulrichii (Coleoptera, Carabidae) were studied in woodland habitats in Hungary. We sampled a beech forest, an oak forest and the adjacent transition zone using pitfall traps, in the Pilis Biosphere Reserve in 2005 and 2006. Generalised linear models were used to explore the impacts of the habitat quality and seasonality on the distribution of this species. We found that the light intensity model explained best the species' activity density pattern, suggesting preference for open oak forest. We also found that the mandible wear was not a good estimator of age in C. ulrichii, but ovarial condition could be used to assess reproductive status. The seasonal activity and life history patterns were similar in the three different habitats for both sexes. Although differences in the total activity density of the species were found, there were no differences either in the seasonal activity patterns, or in the age-composition, or in the reproductive characteristics of C. ulrichii among the studied habitats. C. ulrichii beetles reproduced only once per season in the studied forested habitats.

Beetles are by far one of the most successful groups of insects, with large diversity in terms of number of species. A part of this success is attributed to their elytra, which provide various functions such as protection to their bodies from mechanical forces. In this study, stag beetle (Lucanus cervus) elytra were first examined for their overall flexural properties and were observed to have a localized shape-retaining snap-through mechanism, which may play a possible role in partly absorbing impact energy, e.g., during battles and falls from heights. The snap-through mechanism was validated using theoretical calculations and also finite element simulations. Elytra were also characterized to examine their puncture and wear resistance. Our results show that elytra have a puncture resistance that is much higher than that of mandible bites. The measured values of modulus and hardness of elytra exocuticle were 10.3 ± 0.8 GPa and 0.7 ± 0.1 GPa, respectively. Using the hardness-to-modulus ratio as an indicator of wear resistance, the estimated value was observed to be in the range of wear-resistant biological material such as blood worms (Glyrcera dibranchiata). Thus, our study demonstrates different mechanical properties of the stag beetle elytra, which can be explored to design shape-retaining bio-inspired composites with enhanced puncture and wear resistance.

Seedbank control has been the cornerstone of agricultural management practices. Regulating weeds by using their predators, as a weed control strategy, may be a prerequisite of decreasing herbicide use, and has thus attracted much research investigating the possible contribution of both vertebrates and invertebrates as weed seed predators. Carabid beetles are considered as one of the most important invertebrate seed predators in agroecosystems. We aimed at investigating carabid beetle preferences to a single prey type, seeds ofViola arvensis. We measured the consumption of seeds in 28 species of carabid beetles, under controlled experimental conditions. Two main tribes are identified in tested species,Harpaliniwith 12 species andPterostichiniwith ten species. We found no relationships between species body mass andViola’s seed consumption, nor with the ratio between mandible length and labrum width (ML/LW). However, trends became significant with the ratio ML/LW when restricting these analyses to species that ate at least five seeds. In addition, we detected a positive and significant relationship between consumption rate and occurrence in trapping sessions over the last 3 years. These results are in favor of weed seeds control by carabids. Clear limits of this study are the use of a single seed species and under control conditions. This experimentation calls for additional studies to check for consistencies in consumption against seed species.

It is well-known that population fragmentation and isolation can lead to rapid morphological and functional divergence, with the effect being particularly well-documented in rodents. Here, we investigated whether such a phenomenon could be identified in the Eurasian red squirrel (Sciurus vulgaris), which was once widespread across the majority of Great Britain, but suffered a severe population decline across the 20thcentury, leaving a highly fragmented distribution. The aim was to test for morphological and biomechanical variation of the mandible between the remaining British red squirrel populations. Linear and geometric morphometric methods were used to analyse shape in a sample of over 250 squirrel mandibles from across the UK and Germany. Canonical variates analysis identified significant shape differences between most British red squirrel populations, but particularly between squirrels from Formby and those from other populations. Linear measurements showed that Formby red squirrels have a significantly lower mechanical advantage of the temporalis muscle, indicating that they are less efficient at gnawing. We suggest that this difference may be related to past supplemental feeding of Formby squirrels with peanuts, which are less mechanically resistant than food items that occur naturally in the diet of British red squirrels.

International audience; If domestication has been well studied lately with the recognition of a so-called 'domestication syndrome', the opposite process, feralization, has deserved much less interest. The commensal Western European house mouse (Mus musculus domesticus) lives in close contact to humans, a situation setting it between wild and domesticated animals. However, the house mouse also occurs in non-anthropogenic environments, forming feral populations and hence providing the opportunity to document how feralization may impact its morphology. In this study, three of those 'feral' populations from Orkney, Kerguelen Archipelago and Southern France are compared to Western European commensal populations. The shape and biomechanical properties of the mouse jaws were analysed to assess the impacts of 'feralization' on an organ under major environmental pressures through its feeding function. Mandible shape varied mostly with climate and phylogeny, and feral populations only slightly diverged from their geographically close relatives. In contrast, feral mice shared a biomechanical signature corresponding to a decrease in the superficial masseter/molar mechanical advantage suggesting less performance at molar biting. This is interpreted as a parallel response to a relaxation of environmental pressure, possibly due to diet shift in feral habitats.

The egg-larvae of 890 individuals in 8 species belonging to long palped crane flies of the genus Tipula (Diptera: Tipulidae) were obtained from 17 gravid females captured in Lithuania in 2011–2012. Depending on the species, it took from four days to more than eleven weeks for the eggs to hatch. Of the four instars of larvae for crane flies, the second, third and the last instar larvae are very similar in morphology, while the first instar or egg-larva differs radically. Descriptions and illustrations of the external morphology, chaetotaxy of abdominal segments, characters of head capsules and last abdominal segments are given for the previously unknown first instar larvae of T. (Lunatipula) fascipennis, T. (Pterelachisus) irrorata, T. (P.) pabulina, T. (P.) pseudovariipennis, T. (Yamatotipula) pruinosa and poorly known T. (Beringotipula) unca, T. (L.) vernalis T. (Tipula) paludosa. The differences of the head capsule and last abdominal segment among the first instar larvae of these species are more obvious than in the last instar. Characters of the head capsule such as the shape of the teeth of the mandible, shape of the basal segment of the antenna and number of sensillae on it, shape of hypostomium, arrangement of sensory structures on the labrum and frons, all differ among egg-larvae of Tipula. Sclerotisation and the arrangement of setae on the spiracular field are unique for each studied Tipula species. This is the first study to use head capsule characters to distinguish the larvae of Tipula.

Wood boring is a feature of several insect species and is a major cause of severe and irreparable damage to trees. Adult females typically deposit their eggs on the stem surface under bark scales. The emerging hatchlings live within hard wood during their larval phase, avoiding possible predation, whilst continually boring and tunneling through wood until pupation. A study of wood boring by insects offers unique insights into the bioengineering principles that drive evolutionary adaptations. We show that larval mandibles of the coffee wood stem borer beetle (Xylotrechus quadripes: Cerambycidae) have a highly sharp cusp edge to initiate fractures inArabicawood and a suitable shape to generate small wood chips that are suitable for digestion. Cuticle hardness at the tip is significantly enhanced through zinc-enrichment. Finite element model of the mandible, based on the differential material properties at the tip, intermediate and base regions of the mandible, showed highest stresses in the tip region; these decreased to significantly lower values at the start of the hollow section. A hollow architecture significantly reduces bending stresses at mandibular base without compromising the structural integrity. A scaling model based on a fracture mechanics framework shows the importance of the mandible shape in generating optimal chip sizes. These findings contain general principles in tool design and put in focus interactions of insects and their woody hosts.

Aphodiinae are a large cosmopolitan subfamily of Scarab beetles (Scarabaeoidea: Scarabaeidae), playing an important role during dung decomposition. Many aspects, especially immature stages, of these dung beetles have not yet been recorded due to their comparative small body sizes and lacking of striking rolling behavior. In this study, the third instar larva of Colobopterus quadratus is morphologically described using scanning electron microscopy. The larva is atypical for the combination of following morphological features: (a) the larval antennae are five-segmented; (b) the clypeus bears 4 minute protuberances on dorsal surface; (c) the epitorma on epipharynx is ventrally protuberant; (d) the scissorial area of left mandible is broad and blade-like; (e) the raster is furnished with six glabrous protuberances and two rows of pali arranged in V-shape. Some significant ultra-morphological features were discovered in larval Aphodiinae for the first time. The presence of blade-like incisor on the left mandible implies the potential root cutting ability.

Aquatic predatory insects, like the nymphs of a dragonfly, use rapid movements to catch their prey. Dragonfly nymphs are voracious predators that feed on smaller aquatic organisms. In this study, we examine dragonfly nymph (Libellulidae: Insecta: Odonata)mouthparts that are used in prey capturing and feeding. In particular, we characterise the morphology of the labium and mechanical properties of the mandibles of the nymph. Additionally, we record and analyse the preying mechanism using high-speed photography. The morphological details suggest that the prey capturing mechanism is a complex grasping mechanism with additional sensory organs that might aid in sensing the surroundings. The times taken for the extension and retraction of labial organ during prey capture was 187±54 ms. The Young’s modulus and hardness of the mandibles samples were 9.1±1.9 GPa and 0.85±0.13 GPa. Gradation in the mechanical properties was also observed in the mandible tip regions with increased properties at the tip end. The overall mechanism with its sensory capabilities provides a unique design to develop bioinspired underwater deployable mechanisms.

The cavities of bamboos (Poaceae) are used by various animals. Most of the animals access these cavities either by existing cracks or by excavating bamboos with soft walls or small, thin-walled bamboos. Only a few animals excavate into the cavities of large and thick- and hard-walled internodes of mature bamboos. We studied two lizard beetle species (Coleoptera: Erotylidae: Languriinae), Doubledaya ruficollis and Oxylanguria acutipennis, that excavate into large internode cavities of recently dead mature bamboos and have morphological modifications. We observed that females of D. ruficollis used their mandibles to bore oviposition holes on Schizostachyum sp. (mean wall thickness = 3.00 mm) and O. acutipennis did so on Dendrocalamus sp. (3.37 mm) bamboos. Previous studies suggested that the markedly asymmetrical mandibles and needle-like ovipositors of females in the genus Doubledaya are adaptive traits for excavating hard-walled bamboos for oviposition. Therefore, we measured their mandibular lengths and ovipositor lengths. D. ruficollis females had greater asymmetry in the mandibles and shorter and less-sclerotized ovipositors than females of congeners using small bamboos. In contrast, O. acutipennis females had slightly asymmetrical mandibles and elongated, well-sclerotized ovipositors. Oviposition holes of D. ruficollis were cone-shaped (evenly tapering), whereas those of O. acutipennis were funnel-shaped (tube-like at the internal apex). This suggests that D. ruficollis females excavate oviposition holes using the mandibles only, and O. acutipennis females use both the mandibles and ovipositors. These differences suggest different oviposition-associated morphological specialization for using large bamboos: the extremely asymmetrical mandibles in D. ruficollis and elongated, needle-like ovipositors in O. acutipennis.

Galls induced by insects and mites (insects, hereafter) have been a subject of interest to insect ecologists because of the unusual habit of gall induction and for their tightly connected relationships. These specialist insects and mites have been explored to explain the nature of interactions between them and the plants by entomologists, ecologists and plant physiologists over the last two centuries. However, the questions why only certain insect taxa induce galls on specific species of plants and how galls are induced remain challenging. Whereas several efforts made across the world implicate plant-growth regulators (PGRs) in answering the question on how galls are induced, this article emphasizes the establishment of a metaplasied cell at the location where the tip of the chitinous mandible or ovipositor first hits in the plant. In the light of the differentiation of a metaplasied cell, the earliest plant response, it is but critical to evaluate the physiology of that cell and the ‘new’ physiological events triggered around it, heralding gall initiation. PGRs certainly play a role in gall growth, but only during later stages. This article does not answer the question on how galls are induced. However, it brings to light the gaps that need to be addressed in future in the backdrop of the efforts made over the years. Since we need to deal with the physiological changes that occur in a metaplasied cell and a few adjacent cells, the use of sophisticated optical equipment and pertinent software to achieve a structured and articulate explanation impresses as the way to go.

Stone cells are a physical defence of conifers against stem feeding insects such as weevils and bark beetles. In Sitka spruce, abundance of stone cells in the cortex of apical shoot tips is associated with resistance to white pine weevil. However, the mode of action by which stone cells interfere with growth and development of weevil larvae is unknown. We developed a bioassay system for testing potential effects of stone cells, which were isolated from resistant trees, on weevil larvae. Bioassays using artificial diet and controlled amounts of stone cells focused on physical defence. We evaluated the effects of stone cells on establishment of neonate larvae, mandible wear and changes in relative growth rates of third instar larvae. Establishment of neonates and relative growth rates of third instars were significantly reduced by stone cells. Stone cells appeared to be indigestible by weevil larvae. Our results suggest that stone cells affect weevil establishment and development by forming a physical feeding barrier against neonate larvae at the site of oviposition, and by reducing access to nutrients in the cortex of resistant trees, which contain an abundance of stone cells in place of a more nutrient rich tissue in susceptible trees.