Systenus grossus, Ramos-Pastrana & Merchan-Vargas & Soares, 2024

Ramos-Pastrana, Yardany, Merchan-Vargas, Geraldine Lucia & Soares, Matheus M. M., 2024, First record of the genus Systenus Loew (Diptera: Dolichopodidae) from Colombia, with description of four new species, Zootaxa 5514 (3), pp. 257-272 : 265-267

Systenus grossus sp. nov.

( Figs 4 , 7 )

Diagnosis. Antenna mostly dark brown, except ventral edge of scape and pedicel and a narrow triangular basoventral area of postpedicel orangish yellow ( Fig. 4B ). Postpedicel abruptly narrowed at 1/2 apical, 3.5X as long as basal height; arista short, about 1/2 as long as postpedicel ( Fig. 4B ). Metepimeron brown ( Fig. 4A ). Wing hyaline ( Fig. 4D ). Legs yellow, except basal 2/3 of coxa II, It 5, IIt 3–5 and IIIt 3–5 brown ( Fig. 4A ). Surstylus slightly longer than epandrial capsule, very thickened medially, abruptly narrowed and curved ventrally at apex, 1 digitiform process at basal 1/3 of inner surface ( Fig. 4F, G ).

Description. Male ( Fig. 4 ). Body length: 2.6 mm; wing 1.9 mm. Head ( Fig. 4A, B ). Similar to S. bickeli sp. nov. except as noted: Palpus pale brown with short, black setae at apical 1/2. Proboscis pale brown. Antenna mostly dark brown, except ventral edge of scape and pedicel and narrow triangular basoventral area of postpedicel orangish yellow; postpedicel abruptly narrowed at 1/2 apical, 3.5X as long as basal height; arista short, about 1/2 as long as postpedicel. One row of postocular setae, uppermost 5 setae black, remaining setae pale brown. Thorax ( Fig. 4A, C ). Mostly metallic light green with weak bluish reflections. Metepimeron brown. Legs ( Fig. 4A ). Yellow, except basal 2/3 of coxa II, It 5, IIt 3–5 and IIIt 3–5 brown. Leg I. Podomere ratios: 55, 50, 22/12/9/7/6. Anterior surface of coxa I covered by short vestiture of yellow setae, 3 long yellow setae at apical edge. Femur I clothed by short vestiture of short, brown setae, except ventral surface with yellow setae basal, ventral surface of basal 1/2 mostly bare. Tibia I clothed by short vestiture of yellow setae. Leg II. Podomere ratios: 60, 63, 33/22/16/12/ 8. Anterior surface of coxa II covered by short vestiture of yellow setae, longer at apical 1/2. Femur II clothed by short vestiture of brown setae, except ventral surface mostly bare, apical 1/2 with yellow setae. Tibia II with 2 pairs of antero- and posterodorsal setae at basal 1/4 and at middle, pair of ventral setae at apical 2/4, 1 pair of posterodorsal setae, 1 at basal 1/5 and 1 at apical 1/5 and crown of setae at apex: 1 ventral, 1 anterodorsal, 1 posterodorsal and 1 dorsal. Leg. III. Podomere ratios: 60, 78, 14/30/20/14/8. Lateral surface of coxa III with 1 strong, yellow seta near middle. Femur III with dorsal surface clothed by short vestiture of brown setae, ventral and anterior surface clothed by short vestiture of yellow setae, ventral and posterior surface mostly bare. Tibia III with row of short, strong setae dorsally, starting at basal 1/4 and ending at apical 3/4. Wing ( Fig. 4D ). Hyaline, veins pale brown. R 2+3 nearly straight, R 4+5 and M 1 slightly bowed at apical 6.5/8 and ending parallel at apex. Abdomen ( Fig. 4A, E ). Mostly metallic green, covered by short vestiture of black setae, tergite 1 with long setae at posterior margin, tergite 2–5 with brown medial and lateral bands, tergite 6–7 entirely brown, tergite 7 brown, long and setose, sternite 8 brown. Hypopygium ( Fig. 4F, G ). Surstylus slightly longer than epandrial capsule, very thickened medially, abruptly narrowed and curved ventrally at apex, with 1 digitiform process at basal 1/3 of inner surface ( Fig. 4G ), 3 long setae at basal 1/2 of ventral edge and 1 ribbon-like seta at apex preceded by long seta before apical bend. Epandrial lobe as wide as 1/3 of surstylus at widest point, only with apex strongly curved ventrally, with 1 short digitiform basodorsal process and 2 long setae at ventral edge, 1 basally and 1 apically. Cercus yellow, with rounded swollen base, gradually narrowed at apex, as long as epandrial capsule, about as long as surstylus and covered by short yellow setae.

Female. Unknown.

Type material. HOLOTYPE ♂, labelled: “ COLOMBIA, Caquetá, Florencia, Vda. [Vereda] San Francisco , Fca. [ Finca ] El Recreo , 01º42’24’’N / 75º36’36’’W, 643 m, 01–15.III.2017 / Trampa Malaise en Bosque (Dosel), Y. Ramos-Pastrana Leg. ” ( LEUA) (photographed specimen) . Holotype condition: good, abdomen dissected and stored in microvial with glycerin.

Distribution. Colombia (Caquetá: Florencia) ( Fig. 7 ).

Remarks. The new species is easily distinguished from congeners by the remarkably wide surstylus ( Fig. 4F ) (visible without dissection) and by the digitiform process at basal 1/3 of the inner surface ( Fig. 4G ).

Etymology. From Latin ‘ grossus ’ (= thickness), referring to the shape of the surstylus. Species epithet is to be treated as adjective.

Figures

FIGURE 4. Systenus grossus sp. nov., holotype male (before dissection). A. Habitus, lateral view; B. Head, lateral view; C. Thorax, dorsal view; D. Left wing; E. Abdomen, dorsal view; F. Hypopygium, left lateral view; G. Hypopygium, ventral view, arrows indicating the digitiform processes on inner surface of surstylus.

FIGURE 7. Geographical records of Systenus Loew in Colombia. S. beatae Naglis, 2000; S. bickeli sp. nov.; S. colombiensis sp. nov.; S. flaviatus Naglis, 2000; S. fuscus sp. nov.; S. grossus sp. nov.; S. maculipennis Bickel, 2015; S. naranjensis Bickel, 2015 and S. parkeri Bickel, 2015.