Stilpon variabilis, Grootaert, Patrick & Shamshev, Igor, 2013

Grootaert, Patrick & Shamshev, Igor, 2013, The flies of the family Hybotidae (Diptera, Empidoidea) collected during the Boyekoli Ebale Congo 2010 Expedition in Democratic Republic of Congo, Zootaxa 3603 (1), pp. 1-61 : 57-59

Stilpon variabilis sp. nov.

( Figs. 79–81 )

Material examined. HOLOTYPE, 3 labelled: D.R. CONGO, Yaekela , 5 May 2010, swamp forest (reg. 30015, MS reference as St. 3, leg. P. Grootaert); Holotype / Stilpon variabilis / Grootaert et Shamshev sp. nov. ( RBINS). PARATYPES: 1 Ƥ, Yaekela , 2 May 2010, marsh land (reg. 30004, leg. P. Grootaert); 5 3, 1 Ƥ, Yaekela , 2 May 2010, marsh land (reg. 30006, MS reference as St. 1, leg. P. Grootaert), 1 3 in tray Congo at AB31515399 extracted for DNA; 1 3, Yaekela , 7 May 2010, secondary forest (reg. 30021, leg. P. Grootaert); 1 Ƥ, Yaekela , 7 May 2010, secondary forest (reg. 30021, leg. P. Grootaert); 1 Ƥ, Yaekela , 2-7 May 2010, secondary forest, Malaise trap 1 (reg. 30025, leg. P. Grootaert); 1 3, Kona , 11 May 2010, primary swamp forest (reg. 30032, leg. P.

Grootaert); 2 3, 1 Ƥ, Kona , 11 May 2010, primary swamp forest (reg. 30033, leg. P. Grootaert); 2 3, 1 Ƥ [both dissected], Kona , 13 May 2010, primary swamp forest (reg. 30038, leg. P. Grootaert) one 3 specimen in tray Congo at AB31515301 extracted for DNA; 1 Ƥ, Kona , 15 May 2010, Malaise trap in primary forest, (leg. P. Grootaert); 1 Ƥ, Kona , 16 May 2010, Malaise trap in forest (leg. P. Grootaert).

Diagnosis. Recognised by yellow palpi, hind femur brown on about apical two-thirds. Male: abdomen without gland-like structures.

Description. Length: wing 1.3 mm. Male. Head black in ground-colour. Occiput viewed dorsally subshining, finely greyish pollinose. Vertical bristles short, black. Frons sublinear with slightly divergent sides above, broad, entirely tomentose. Anterior ocellar bristles minute. Antenna with scape and pedicel dark brown, postpedicel and stylus slightly paler. Palpus yellow, with long, black, subapical seta (as long as palpus).

Thorax black in ground-colour. Scutum viewed dorsally subshining, entirely finely tomentose. Postpronotal bristle long, inclinate. Acrostichal and dorsocentral setae undifferentiated, complete posteriorly.

Legs largely yellow, fore coxa with rounded brownish spot anteriorly near base, hind femur brown on about apical 2/3. Fore femur markedly thickened, with row of very short anteroventral and row of moderately long posteroventral setae. Fore tibia spindle-like, with ordinary setation. Mid femur slender, with 2 black, moderately long, spine-like, ventral bristles on about middle (colour of basal spine apparently varying), 2 longer, thinner, yellow bristles near base and 1 long black anterior subapical bristle. Mid tibia with row of black, anteroventral spinules. Hind trochanter lacking spinules. Hind femur (viewed laterally) evenly thickened toward middle, with row of short anteroventral bristles becoming somewhat longer apically. Hind tibia with unmodified posterior apical comb, clothed with ordinary setulae. Hind basitarsus somewhat thickened.

Wing normally developed, covered with uniform microtrichia; uniformly infuscate, somewhat darker on about basal half of cell r2+3. Costal vein with moderately long setulae along anterior margin; costal bristle brown, short. Vein R 2+3 straight, about 2.0 times as long as Rs. Distance between apices of veins R2+3 and R4+5 nearly as long as distance between apices of veins R l and R2+3. Veins R4+5 and M l+2 divergent and arcuate in apical part. Halter with black knob and yellow stem.

Abdomen with tergites very weakly sclerotised (except segment 8), with scattered minute setulae; sternites 2–6 divided medially, sternite 8 with long posteromarginal setae. Gland-like structures not prominent. Terminalia ( Fig. 79–81 ) rather large, brown. Cerci separated; left cercus unbranched, rather subrectangular, lacking spines, with 1 very long subbasal and several shorter unmodified setae; right cercus unbranched, short, subtriangular, lacking spines, with 2 very long subapical and 3 shorter unmodified setae. Epandrium ( Fig. 80 ) completely divided. Right surstylus ( Fig. 79 ) bearing 4 long subbasal and several shorter unmodified setae, lacking spines. Left epandrial lamella small, fused to hypandrium, with 4 short setae in apical part. Left surstylus ( Fig. 81 ) represented by 2 sclerites, with upper lobe undivided and lacking surstylar comb; upper lobe subrectangular with deep apical excision, lacking spines, with several unmodified setae of different lengths; lower lobe subrectangular, narrowed apically, with 3 short unmodified setae. Phallus short.

Female. Mid femur with somewhat longer, brownish yellow setae on about middle. Mid tibia with somewhat longer anteroventral spinule-like setulae. Abdomen with tergites completely de-sclerotised (except segment 8), brownish yellow dorsally, with scattered minute setulae; sternites somewhat stronger sclerotised, sternites 2–6 divided medially. Terminalia rather elongate; segment 8 modified, tergite 8 almost entirely pale yellow (except narrow anterior margin), fused with sternite 8 anteriorly; sternite 8 brown; cercus brownish yellow.

Etymology. The specific epithet “ variabilis ” refers to variation in colour of the hind femur and the size of the male genitalia.

Distribution. D.R. Congo.

Remarks. The new species differs from S. lomaense in having its hind femur brown on apical half to twothirds (vs. entirely yellow). Also, it can be distinguished from S. congoensis sp. nov. by yellow palpi and male abdomen without gland-like structures. This species is polymorphic because several important characters vary in a broad range: the extent of brownish black colouring of the tip of the hind femur ranges from half to two-thirds its length; ventral spinules on mid tibia vary from pale to black; the mid femur can have 1 or 2 black ventral bristles; the size of the male genitalia ranges from rather small to large.

Figures

FIGURES 79 – 81. Stilpon variabilis sp. nov. 79. Right epandrial lamella; 80. Epandrium with cerci; 81. Left surstylus.