Systenus maculipennis Bickel

Bickel, Daniel J., 2015, The Costa Rican Systenus Loew (Diptera: Dolichopodidae): rich local sympatry in an otherwise rare genus, Zootaxa 4020 (1), pp. 169-182 : 174

Systenus maculipennis Bickel sp. nov.

( Figs 1 e, f)

Type material. HOLOTYPE ♂, COSTA RICA: Guanacaste: 3 km SE Rio Naranjo, 18-28.IV.1993, F.D. Parker ( LACM, ex. EMUS; LACM Ent 329996); PARATYPE ♂, same but 22-24.VII.1992 ( LACM Ent 329997).

Description. Male: body length: 2.8 mm; wing 2.7 x 0.9 mm ( Fig. 1 e); similar to S. tenorio except as noted: Head: palpus yellow with short black setae and strong apical seta; proboscis yellowish; scape and pedicel yellowish, postpedicel mostly yellow on basal third, but brown distally; postpedicel subrectangular basally and abruptly narrowed to elongate tapering point in distal half, and covered with short pubescence, with antenna overall about 3 ½ times as long as basal width; short apical arista present. Legs: CI entirely yellow; CII and CIII dark brown basally, but distal eighth pale yellow; all trochanters and remainder of legs yellow; CI and CII with white anterior setae and shorter vestiture, CIII with strong while lateral seta at ½; major leg setae black; I: 4.0; 3.7; 1.7/ 0.9/0.7/0.4/0.3; leg I bare of major setae; TI with mostly ivory colored (not usual black) short vestiture (MSSC); II: 4.1; 4.6; 2.3/ 1.7/ 1.0/ 0.6/ 0.4; TII with strong ad seta and weaker basally offset pd seta at ¼, and without any setae near 2/3, and with apical ring of ad, pd, av and ventral seta; III: 4.7; 5.7; 1.0/ 2.2/; 1.2/ 0.8/ 0.4; TIII with row of 5 black dorsal setae from 1/5 to 4/5, and with apical ring of dorsal, ad and av seta. Wing: hyaline but with apical brown maculation, and with wing modified so that membrane is reduced posteriad of distal vein M, so that M forms posterior margin adjacent to the brown maculation (MSSC) ( Fig. 1 e); vein M diverging from R4+5 with two veins subparallel beyond dm-cu crossvein and not at all bowed (MSSC); M joining costa just behind wing apex; CuAx ratio: 1.1; lower calypter pale yellow with yellowish marginal setae; halter yellow. Abdomen: black with metallic bronze-green reflections and with dusting of grey pruinosity; posterior margin of tergite 1 with posterior row of long black setae, tergites otherwise covered with short black vestiture; sternites 2-6 membranous or only weakly sclerotised, somewhat recessed; hypopygium ( Fig. 1 f) dark brown with yellow surstylus and cercus; epandrium ventrodistally extended and up curved, and bearing long ventral seta; surstylus basally wide and expanded distally, with group of ventral setae, and narrowed to curved digitiform projection; cercus with wide base, and extending distally as swollen digitiform projection covered with short yellow setae. Female: unknown.

Remarks. Systenus maculipennis is known from two males taken at the Rio Naranjo site, Costa Rica, in the months of April and July. The wing apex of males is brown, and the posterior membrane is reduced near the apex, so that vein M itself forms the posterior margin adjacent to the brown maculation (MSSC) ( Fig. 1 e). This modification has affected the CuAx ratio which is near 1.1, whereas in most Systenus species the ratio is near 0.6. As well, the male postpedicel has the basal subrectangular section mostly yellow while the tapering distal half is dark brown. This species also has ivory colored vestiture on tibia I.

Etymology. The specific epithet “ maculipennis ” is Latin, and refers to the brown spot on the male wing.

Figures

FIGURE 1. Systenus tenorio sp. nov. (holotype): a. male habitus, left lateral (terminalia removed); b. hypopygium, left lateral. S. flavifemoratus sp. nov. (holotype): c. male habitus, right lateral; d. hypopygium, left lateral. S. maculipennis sp. nov.: e. male habitus, left lateral (terminalia removed); f. hypopygium, left lateral. Abbreviations: cer, cercus; epan, epandrium; hyp, hypandrium; ph, phallus; st, sternite; sur, surstylus; tg, tergite; 6, 7, 8, abdominal segments.