Hercostomus acutiformis Negrobov, Kumazawa & Tago

Negrobov, O. P., Kumazawa, T., Tago, T. & Sato, M., 2016, New species of Hercostomus Loew, 1857 (Dolichopodidae, Diptera) from Japan, Zootaxa 4158 (1), pp. 65-80 : 66

Hercostomus acutiformis Negrobov, Kumazawa & Tago sp. nov.

( Figs 1 A–F, 8A)

Hercostomus sp. № 9t. Tago, 2010: 9.

Type material. HOLOTYPE Ƌ, labeled: Japan, Saitama pref., Mameyakibachi, Ootaki, Chichibu City , 7.vii.2008, leg. T. Tago ( OMNH) . PARATYPES: 2 Ƌ, Japan, Saitama pref., Mameyakibachi, Ootaki, Chichibu City , 7.vii.2008, 5.06.2010, leg. T. Tago (1 Ƌ OMNH, 1 Ƌ VSU) .

Description. Male. Head with frons dull green with dense white pollinosity. Face green with dense white pollinosity, without hairs, not reaching lower eye margin, middle part of face narrower than postpedicel width. Postocular setae black. Proboscis and palpus black with dark hairs. Antenna ( Fig. 1 E) black. Postpedicel pointed apically, longer than wide. Stylus placed on dorsal side of postpedicel, with short hairs. Ratio of 1st and 2nd segments of stylus: 3.4: 4.8. Ratio of postpedicel length to width and stylus length: 4.4: 2.4: 8.2. Thorax black with metallic tinge, without pollinosity. Pleura black, with slight grey pollinosity. Propleuron with 1 black seta below, without hairs above. Scutellum bare above, with 2 strong black lateral setae and small marginal hairs. Legs yellow, except most of mid coxa, hind coxa at base, apical 2/3 of hind tibia, fore and hind tarsi, apex of fore tibia and most of mid tarsus dark. Segments of tarsi simple, not widened. Femora without long hairs below. Fore femur without preapical setae. Fore tibia without long apicoventral seta, with 2 short anterodorsal and 1 short posterodorsal setae. Segments of fore tarsus with short hairs. Ratio of length of fore tibia and tarsomeres (from 1st to 5th): 5.7: 3.1: 1.9: 1.4: 1.0: 0.8. Mid femur with 1 short preapical outer seta and 1 short preapical inner seta. Mid tibia with 2 long anterodorsal, 2 posterodorsal and 2 posteroventral setae. Tarsomere 1 of mid tarsus without setae. Ratio of length of mid tibia and tarsomeres (from 1st to 5th): 8.2: 4.5: 2.5: 2.1: 1.4: 0.9. Hind coxa with 1 black outer seta. Hind femur with 1 preapical outer seta. Hind tibia thickened apically, with 2 long anterodorsal, 3 long posterodorsal and 5–6 short anteroventral setae. Ratio of length of hind tibia and tarsomeres (from 1st to 5th): 8.9: 3.1: 3.1: 3.6: 1.5: 0.9. Tarsomere 1 of hind tarsus with black curved claw-like process at base on posteroventral side ( Fig. 1 F). Wing darkened. Costal vein without thickening at tip of R1. Ratio of costal section between R2+3 and R4+5 to that between R4+5 and M1+2—2.3: 0.7. R4+5 and M1+2 convergent apically. Ratio of m-cu to apical part of M3+4—1.6: 4.6. Anal angle obtuse. Calypter yellow with black cilia. Halter yellow. Abdomen black with green tinge, bright, with black setae and hairs. Abdominal segment 8 black. Epandrium black, oval, longer than wide ( Figs 1 A, E). Phallus and hypandrium ( Figs 1 C, D) yellow. Cercus shorter than epandrium, widened apically, with long process on dorsal side, with long black hairs. Female. Unknown. Length (mm): body: 2.8–2.9, wing: 2.8–3.0.

Etymology. The species is named for the claw-like process on the male hind tarsus.

Remarks. According to Stackelberg (1934) the new species is included in the third group of Hercostomus (femora yellow, postocular setae black). In the key to Palaearctic species (Selivanova et al. 2012), the new species runs to Hercostomus gansuensis Yang, 1996 , and can be distinguished from the latter by the morphology of the hypopygium and further features:

- Tarsomere 1 of hind tarsus with long claw-like process at apex ( Fig. 1 F). Mid tibia with 2 anterodorsal, 2 posterodorsal and 2 posteroventral setae. Tarsomere 1 of hind tarsus approximately equal to tarsomere 2...... Hercostomus acutiformis sp. nov. - Tarsomere 1 of hind tarsus without claw-like process at apex. Mid tibia with 3 anterodorsal, 2 posterodorsal and 1 ventral setae. Tarsomere 1 of hind tarsus approximately 1.5 times shorter than tarsomere 2.......... Hercostomus gansuensis Yang

In the key to Chinese species ( Yang et al. 2011), the new species runs to Hercostomus apicilaris Yang & Grootaert, 1999 , but can be distinguished from that species by the following features:

- Mid tibia with 2 anterodorsal setae. Epandrium almost round, slightly longer than wide, oval on ventral side, without depression ( Fig. 1 A). Cercus with oval process at apex on ventral side (Fig. B)............... Hercostomus acutiformis sp. nov. - Mid tibia with 3 anterodorsal setae. Epandrium elongate, almost 1.5 times longer than wide, with depression on ventral side. Cercus with triangular process at apex on ventral side....................... Hercostomus apicilaris Yang & Grootaert

Figures

FIGURE 1. Hercostomus acutiformis sp. nov. (A) hypopygium, left lateral view; (B) right cercus, ventral view; (C) hypopygium, ventral view; (D) epandrial lobe, surstylus, postgonite, left lateral view; (E) antenna, lateral view; (F) hind tibia and hind basitarsus, lateral view.