COPESTYLUM TETETZOI MARCOS, HANCOCK & ROTHERAY SP. NOV. Adult: Male holotype: face with lateral margins inflated and sharply tapered from just above margin of mouth (view from in front). Face yellow with a narrow (about as wide as antennal bases are apart) black, mid-dorsal vitta extending from the base of the antennae to the margin of the mouth and face yellow haired. Tubercle slight and below mid point between antennae and mouth. Frons black with black hairs. Lateral vittae black reaching mouth and genae black and pale haired (Fig. 3). Antennae dark yellow and arista densely pilose with short, incurved hairs and basoflagellomere dorsally not excavated and more than 3¥ as long as broad. Ocellar triangle black with long black hairs and suture same length as ocellar triangle. Eyes black haired, hairs longer at top of head and reaching lower margin. Eye hairs denser and darker in the middle of the eye forming a vertical, black stripe. Ground colour of mesonotum black except for uniformly pale yellow lateral margins and a medial pair of triangular shaped yellow markings on the posterior margin. Mesonotum with mostly long hairs with a few shorter ones on the posterior margin. Longer hairs about 2¥ as long as shorter hairs. Hairs white except for some black hairs on the lateral margins and short, black hairs on the posterior margin. Mesonotum with a pair of dusted stripes dorsocentrally ending before the transverse suture. Scutellum yellow with short black hairs and long pale hairs. Pleurae black, only pale on the dorsal part of posterior anepisternum and with long white hairs on posterior anepisternum, anepimeron, and katepisternum. Wings hyaline, without markings or microtrichia. Legs black haired and blackish with knees and basal two thirds of tibiae yellow. Sternites 1, 2, and 3 yellow and pale haired, fuscous medially, remaining sternites black and black haired except anterior corners of sternite 4 with a pair of yellow spots. Tergites black except tergite 2 with yellow triangular spots tapering almost to a point towards the medial line and reaching the side margins. Tergite 3 with a pair of semicircular spots in anterior two thirds and not reaching side margins. Tergite 4 with a pair of yellow bars on the anterior margin and not reaching the side margins. Tergite 1 pale haired except for posterior lateral margins. Tergite 2 pale haired except black haired on posterior third and medial line. Tergite 3 black haired except for pale hairs on anterolateral margins. Male genitalia: epandrium subrectangular in shape; surstylus square in shape, truncate at apex; hypandrium not inclined backwards, straight in lateral view; superior lobe with a hook-like, sharply tapered apex (Figs 14, 15). Female: Similar to holotype male except: frons with one medial and two lateral grooves; width of vertex about one fourth width of head. Length: Body 8.0–9.0 mm; wing 8.0– 9.5 mm (N = 8). Larva and puparium (Fig. 21): Anterior fold with a wide spicule band extending from just above the antennomaxillary organs to the apex. Spicules confined to the extreme ends of the longitudinal folds of the prothorax, only one or two further along between the folds. Crochets of metathoracic prolegs forming a w-shaped band. Metathorax with lateral folds bearing broad setae at sensilla 4 and 5. Anal lobe with spicules. Posterior breathing tube with AP 0.8¥ length of TR, with light punctures and not tapered. Pupal spiracles about 0.85¥ length of AP. Material examined: holotype: male with puparium MEXICO, Puebla, Tehuacán, Jardín Botánico, 1590 m (18°19′58″N, 97°27′28″W), 7.vii.1999, ex live decaying Neobuxbaumia tetetzo (F.A.C. Weber) Backeberg 1938 (Cactaceae), collected by M. A. M. (CIBIO). Paratypes: 2 ♂ and 3 ♀ with puparia, same data as holotype (CIBIO); 1 ♂, MEXICO, Puebla, San Juan Raya, 9.vii.1999, collected by M. A. M. (CIBIO), ex decaying Cactaceae; 1 ♀, MEXICO, Oaxaca, Santiago Dominguillo, 14.vii.1999, collected by M. A. M. (CIBIO), ex decaying Cactaceae; 1 ♀ MEXICO, Puebla, Zapotitlán Salinas, Jardín Botánico, 10.vii.1999, ex live decaying (Cactaceae), collected by E. G. H. (HM); 1 ♀, one puparium MEXICO, Oaxaca, Santiago Dominguillo 14.vii.1999 E. G. H., M. A. M., G. E. R. ex decaying stem of Ferocactus latispinus var. spiralis (Karw. ex Pfeiller) Taylor 1984; 3 ♂, 4 ♀, seven puparia, one larva MEXICO Tehuacán, Puebla Zapotitlán, Salinas, Jardín Botánico 7.vii.1999 E. G. H., M. A. M., G. E. R. ex decaying stems of fallen N. tetetzo; 1 ♂, one puparium MEXICO, Tehuacán, Puebla, Zapotitlán, San Juan Raya (El Salado) 9.vii.1999 E. G. H., M. A. M., G. E. R. ex decaying stem of fallen Neobuxbaumia mezcalaensis (Bravo) Backeb 1941 (Cactaceae) (NMS). Etymology: The name tetetzoi refers to the cactus species Neobuxbaumia tetetzo from which the holotype was reared. Taxonomic notes: The adult of this species can be easily separated from other Marginatum group adults by the male genitalia, black frons, and wings hyaline without brown spots. The larva and puparium of C. tetetzoi is similar to C. bequaerti and C. lentum in having an AP which is shorter than the width of the TR. The nontapering punctured AP separate C. tetetzoi from C. lentum and the absence of anterior spiracles separates it from C. bequaerti., Published as part of Rotheray, Graham E., Marcos-García, Maria-Angeles, Hancock, Geoff, Pérez-Bañón, Celeste & Maier, Chris T., 2009, Neotropical Copestylum (Diptera, Syrphidae) breeding in Agavaceae and Cactaceae including seven new species, pp. 697-749 in Zoological Journal of the Linnean Society 156 (4) on pages 709-710, DOI: 10.1111/j.1096-3642.2008.00503.x, http://zenodo.org/record/5443474