Systenus divericatus 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 : 176-178

Systenus divericatus Bickel sp. nov.

( Figs 3 a, b)

Type material. HOLOTYPE ♂, COSTA RICA: Guanacaste: 3 km SE Rio Naranjo, 21—28.II.1992, F.D. Parker ( LACM, ex. EMUS; LACM Ent 320000).

Description. Male: body length: 2.3 mm; wing 2.2 x 0.8 mm ( Fig. 3 a); similar to S. tenorio except as noted: Head: palpus yellow with short black setae and strong apical seta; proboscis yellowish; antenna mostly dark brown but postpedicel yellowish laterally near base; postpedicel elongate, triangular tapering gradually, covered with short pubescence, more than 3 times as long as basal width, and with short apical arista. Legs: CI yellow; CII and CIII mostly dark brown, but distal eighth yellow; all trochanters yellow; femora mostly yellow but distal quarter of FIII infuscated; remainder of legs mostly yellow; TIII and tarsomeres III mostly with white cuticle (MSSC): CI and CII with white anterior setae and shorter vestiture, CIII with strong while lateral seta at ½; major leg setae black; I: 3.1; 3.0; 1.6/ 0.6/ 0.4/ 0.3/ 0.2; leg I bare of major setation; TI and tarsus I only covered with ivory colored vestiture (MSSC); II: 3.6; 3.8; 2.0/ 1.3/distal tarsomeres missing; TII with strong ad seta and weaker pd seta at ¼, and short anterior, long ad and short pd seta near 2/3, and with apical ring of ad, pd, av and ventral seta; III: 3.8; 4.6; 0.8/ 1.8/ 1.0/ 0.7/ 0.5; TIII with 4 spaced short black dorsal setae, and with apical ring of dorsal, ad and av seta. Wing: hyaline; R2+3 and R4+5 diverging from base, R2+3 joining costa near 7/8, and R4+5 joining costa almost at wing apex; vein M diverging from R4+5 from base, and not becoming subparallel, but with M continuing to diverge to join costa well behind wing apex, and with distal outward bend causing small bump on posterior wing margin (MSSC); costa between apex of R4+5 and M almost straight (MSSC); CuAx ratio: 0.7; lower calypter pale yellow with yellowish marginal setae; halter yellow. Abdomen: segment 7 forming elongate peduncle, with sternite 7 glabrous and tergite 7 covered with same black vestiture as preabdomen; sternite 8 forming cap-like cover over hypopygial foramen; hypopygium ( Fig. 3 b) dark brown with yellow surstylus and cercus; epandrium ventroapically truncated; surstylus as elongate digitiform projection which is apically swollen, and bearing apical seta; cercus elongate and flagellate, and bearing elongate pale setae along length. Female: unknown.

Remarks. Systenus divericatus is known from a single male taken at the Rio Naranjo site, Costa Rica in February. It has the diagnostic male character with veins R4+5 diverging distally with vein M and apically bent (MSSC), a black tapering postpedicel, and coxa I and remainder of legs mostly yellow except femur III infuscated along the distal quarter. Like many Costa Rican Systenus species, tibia and tarsus I have ivory colored vestiture. Etymology. The specific epithet “ divericatus ” is Latin and refers to the diverging veins R4+5 and M.

Figures

FIGURE 3. Systenus divericatus sp. nov. (holotype): a. male habitus, left lateral; b. hypopygium, left lateral. S. zurqui sp. nov.: c. male habitus, left lateral; d. hypopygium, left lateral.