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.