Sclerocoelus rostrum, Kuwahara & Marshall & Paiero, 2025

Kuwahara, Gregory K., Marshall, Stephen A. & Paiero, Steven M., 2025, A revision of the genus Sclerocoelus Marshall (Diptera: Sphaeroceridae), European Journal of Taxonomy 979, pp. 1-277 : 105-106

Sclerocoelus rostrum sp. nov.

urn:lsid:zoobank.org:act:631F57AF-83C7-4E58-8BFC-FE9533B43378

Figs 131–132

Etymology

This name refers to the beak-like surstylus and triangular subcercus (from the Latin ‘ rostrum ’, meaning ‘beak, bill, snout’).

Material examined

Holotype

MEXICO • ♂; Hidalgo, 5 km N of Zicualtipán, Highway 105; 2500 m a.s.l.; 23 Jun. 1986; M. Sörensson and B. Mårtensson leg.; MZLU.

Description

BODY ( Fig. 131A ). Length 2.5 mm. Head dark brown, lower third of frons orange; face, gena, and antennae orange-brown. Frontal width 2.2× frontal height. Three pairs of strong interfrontal bristles surmounting a very fine fourth pair; anterior orbital 0.6–0.7× length of posterior. Palpus brown. Eye large, greatest height about 4.0× shortest genal height. Thorax dark brown, scutum with paler lateral edges. Two pairs of dorsocentral bristles (anterior pair distinct, 0.4× length of posterior pair) separated by 8–9 rows of acrostichal setulae. Membrane around prosternum bare. Legs brown, fore and hind femora darker. Fore femur with three large ventral preapical setae. Ventral surface of male mid tibia with two rows of stout setae in apical half. Wing slightly infuscate. CS2 0.8× CS3. Halter pale brown.

MALE ABDOMEN ( Figs 131B–C , 132 ). Dark brown, posterior edges of tergites slightly desclerotized. T2–5 and S2–4 uniformly long-setose with large posterolateral setae. S5 rectangular, 2.0× length of S4, sparsely setose with large, dark, rectangular, slightly bulging posteromedial patch of dense setulae flanked by pale setose areas. Anterior flange of S6+7 very large, 1.2 × as long as wide, extending to anterior margin of S4. Sclerite A dark, unmodified; sclerite B thin, arched; sclerite C reduced, indistinct; sclerite D dark, broad, arising from left side of posteromedial process of S5; sclerite E dark, elongate; sclerite F large, subtriangular with a narrow apicoventral process on left side; sclerite G dark, club-shaped, fused to anterior edge of sclerite F; ring sclerite well sclerotized, outer side much thicker than inner side, and with a short posteroventral lobe. Epandrium large, 0.8× length of S8, height 1.7× maximum length and 0.8× maximum width, uniformly setose; perianal pads weakly developed but setulose. Pseudocercus well developed, narrowly fused with posteroventral corners of epandrium, and bearing three setae; halves of subepandrial sclerite broad, very strongly arched, expanded and broadly fused medially. Subcercus projecting posteriorly, elongate, apically flattened and twisted, anteriorly with a short, dark, basal lobe. Hypandrium with thick, laterally flattened, Y-shaped anteromedial apodeme. Surstylus large, subtriangular, apex slightly curled ventrally, outer surface setose, inner surface with a dark anterodorsal lobe. Postgonite long, mushroom-shaped, greatly expanded anteriorly and posteriorly in distal half, posteroventrally striate and curled laterally. Phallapodeme very large, dark, apex dorsoventrally flattened; basiphallus small with a short, triangular epiphallus; distiphallus large, with a short, heavily sclerotized dorsal sclerite and a pair of long, heavily sclerotized, J-shaped ventrolateral sclerites.

FEMALE ABDOMEN. Female unknown.

Distribution

Neotropical: Mexico.

Remarks

Sclerocoelus rostrum sp. nov. is known from only a single male specimen that differs from all congeners in having a triangular, beak-like surstylus, large, triangular subcercus, postgonite broadly expanded apically, and S5 with a stout posteromedial patch of dense setae. It is one of eight congeners found in Mexico, and one of two known only from Mexico.

Figures

Fig. 131. Sclerocoelus rostrum sp. nov., male holotype (MZLU). A. Habitus, lateral view. B. Terminalia, posterior view. C. Terminalia, lateral view. Abbreviations: epa= epandrium; pc=pseudocercus; sc =subcercus; se =subepandrial sclerite; ss =surstylus. Scale bars: A=1.0 mm; B–C = 0.25 mm.

Fig. 132. Sclerocoelus rostrum sp. nov., male holotype (MZLU). A. Aedeagus and associated structures, lateral view. B. S5 and genital pouch, ventral view. Abbreviations: bp =basiphallus; dp =distiphallus; epi= epiphallus; hyp=hypandrium; pg =postgonite; ph =phallapodeme. Scale bars: A=0.13 mm; B=0.25 mm.