Cerodontha ( Cerodontha ) nigricornis Becker

Boucher, Stéphanie & Wheeler, Terry A., 2014, Neotropical Agromyzidae (Diptera) of the Mission Géodésique de l’Équateur: Becker (1920) revisited, Zootaxa 3779 (2), pp. 157-176 : 165

Cerodontha ( Cerodontha) nigricornis Becker

( Figs. 25–27 )

Cerodonta nigricornis Becker 1920: 212 .

Cerodontha nigricornis, Spencer 1963: 332 ; Sasakawa 1992b: 815.

MNHN specimen. Holotype ♀: Ecuador: Casitagua, alt. 3500 m, P. Rivet, 1903.

Additional material examined. Argentina: Jujuy, La Quiaca, 23.x.68, 3500 m, L.E. Pena ( 1 ♂: CNC).

Diagnosis. This species can be distinguished from other Neotropical species of Cerodontha (Cerodontha) by the following combination of characters: the presence of acrostichals; femora yellow only at knees; first flagellomere strongly angulate but without spine; presence of only 1 ors and sometimes 1 weaker ori; orbit with dense patch of white pubescence anteriorly; large size (wing length over 3.0 mm); and the shape of the male genitalia.

Description. Frons width 0.30 mm; ratio of frons width to eye width 1.4–1.5 (measured in dorsal view); orbit 0.22–0.27 times width of frons (including orbits) at midpoint; parafacial well developed, forming large ring (cheek) below eye; 1 reclinate ors; and 1 fine, pale (almost invisible in male specimen), proclinate and slightly inclinate ori; orbital setulae forming dense white patch of hairs anteriorly (overlooked in original description); first flagellomere elongated, projecting dorsoapically (but without spine), with short pubescence apically; arista slightly shorter than maximum eye height and with short pubescence; gena deep, extended at rear; gena height at midpoint: 0.38 times maximum eye height; upper margin of clypeus narrow, rounded; eye bare or at most with short scattered pubescence. One presutural and three postsutural dorsocentrals; acrostichals few, in 2 rows; prescutellar acrostichal seta absent; scutellum with only one pair of apical setae; notopleuron with 2 setae; postpronotum with 1 strong seta and 1 (in holotype) to 4 setulae; anepisternum with 1 strong seta on posterior margin a little above midpoint, and no additional seta ( holotype) or 1 small seta (male) underneath; fore femur with 2 strong lateroventral setae near apex, 1 strong lateral seta basally and 1 or 2 strong dorsal setae near apex; fore and mid tibiae without lateral seta; wing length 3.0 mm in male and 3.8 mm in female; M1+2 ending at wing tip; costa extending to M1+2; last section of CuA1 0.70–0.77 times length of penultimate.

Colour. Frons completely yellow including most of orbits, except brownish under ors; both vt on brown, but vti at limit of yellow ground; hind margin of eye brown for a short distance beyond vte; face yellow; all antennal segments brown; palpus brown; margin of clypeus brown. Mesonotum and scutellum mat greyish or greyishbrown; postpronotum yellow with central brown patch; postpronotal seta on yellow ground; notopleuron yellow with very small brown marking at anteroventral corner; anepisternum mostly brown excluding yellow posterodorsal corner; katepisternum completely brown; katatergite prominent and yellow; calypter white with margin and fringe pale brown; halter white; legs, including coxae, brown, with knees yellow for about 1/5 of femur length (measurements taken on fore femur).

Male genitalia. Phallus weakly sclerotized, long and straight for most of its length but curving ventrally near apex; distiphallus fused for entire length except narrowly divided behind apex ( Fig. 27 ); surstylus elongated, projecting ventrally, bearing multiple spines on ventral surface; ejaculatory apodeme small with fan-shaped blade.

Comments. This species was previously known from a single Ecuadorian female specimen ( Becker 1920; Spencer 1963; Sasakawa 1992b; Martinez & Etienne 2002). Becker (1920) did not explicitly designate a holotype in the original publication and the specimen does not bear a type label, but because no other type specimens are known to exist, we consider this specimen to be the holotype, fixed by monotypy. We have added a label to that effect.

One additional specimen was examined from Argentina and represents the first documented male. This species is most similar to Cerodontha ( C.) chilensis Spencer and Cerodontha ( C.) magellani Spencer , both described from Chile ( Spencer 1982), but differs in having a characteristic white patch of proclinate orbital setulae, larger size, and a slightly different curvature of the phallus. Additional material agreeing with the description of this species has also been collected by M. v. Tschirnhaus in the high Andes ( 4000–5000 m elevation) of northern Chile (M. von Tschirnhaus, pers. comm.).

Figures

FIGURES 25 – 27. Cerodontha nigricornis Becker, (25) phallus, lateral (before dissection), (26) phallus, lateral, (27) phallus, ventral. Scale bars = 0.05 mm.