Hercostomus falcilis 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 : 67-69

Hercostomus falcilis Negrobov, Kumazawa & Tago sp. nov.

( Figs 2 A–C, 8B)

Hercostomus sp. № 10t. Tago, 2012: 6.

Type material. HOLOTYPE Ƌ, labeled: Japan, Saitama pref., Irikawa, Ootaki, Chichibu City , 28.vii.2012, leg. T. Tago ( OMNH) . PARATYPES: 1 Ƌ, Japan, Saitama pref., Irikawa, Ootaki, Chichibu City , 28.vii.2012, leg. T. Tago (1 Ƌ OMNH, 1 Ƌ VSU) .

Description. Male. Head with frons dull with dense white pollinosity. Face white, without hairs, not reaching lower eye margin. Middle part narrower than postpedicel width. Proboscis yellow. Palpus brown, with black hairs and 1 black seta. Antenna ( Fig. 2 C) black. Postpedicel pointed apically, longer than wide. Stylus placed at middle of dorsal side of postpedicel, with short hairs. Ratio of the 1st and 2nd segments of stylus: 5.4:.5.3 Ratio of postpedicel length to width and stylus length: 7.8: 3.6: 10.7. Postocular setae black. Thorax green with metallic tinge and yellow on edges anteriorly, without pollinosity. Pleura yellow, with dark metallic green spot on pteropleuron. Propleuron with 1 black seta below and group of yellow hairs above. Scutellum bare above, with 2 strong black lateral setae and small marginal hairs. Legs yellow, tarsi darkened at apex. Segments of tarsi simple, not widened. Femora without long hairs below. Fore femur without preapical setae. Fore tibia without long apicoventral seta, with 1 anterodorsal and 2 short posterodorsal setae, with row of small anteroventral hairs in upper 2/3. Ratio of length of fore tibia and tarsomeres (from 1st to 5th): 6.3: 3.7: 2.3: 1.6: 1.0: 0.9. Mid femur with 1 preapical outer seta and 1 preapical inner seta. Mid tibia with 3 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): 9.3: 4.5: 2.8: 2.5: 1.7: 0.9. Hind coxa with 1 black outer seta. Hind femur with 1 preapical outer seta. Hind tibia with 3 long anterodorsal, 3 long posterodorsal and 5 short anteroventral setae. Ratio of length of hind tibia and tarsomeres (from 1st to 5th): 10.9: 3.1: 4.0: 2.6: 1.7: 1.4. Tarsomere 1 of hind tarsus with several small ventral setae. Wing darkened. Costal vein without thickening at tip of R1. Ratio of costal section between R2+3 and R 4+5 to that between R4+5 and M1+2—2.6: 0.8. R4+5 and M1+2 convergent apically. Ratio of m-cu to apical part of M3+4—1.8: 2.5.

Anal angle obtuse. Calypter yellow with black cilia. Halter yellow. Abdomen mostly yellow, with black setae and hairs, segment 1 yellow with green spot in the middle of posterior part, tergites 2–4 with yellow spots laterally, abdominal sternites yellow, abdominal segment 8 yellow. Epandrium ( Figs 2 A, B) yellow at base, oval, longer than wide. Cercus oval, yellow at apex, with darkened apex, phallus black. Cercus longer than wide. Female. Unknown. Length (mm): body: 2.8–2.9, wing: 2.8–2.9.

Etymology. The species is named in reference to the shape of the antennae.

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 flaviventris Smirnov & Negrobov, 1977 , and can be distinguished from the latter by the morphology of hypopygium and further features:

- Postpedicel obtuse apically, a little longer than wide. Abdominal tergites 3–5 green................................................................................................ Hercostomus flaviventris Smirnov & Negrobov - Postpedicel pointed apically, twice longer than wide. Abdominal tergites 3–5 with yellow spots laterally.............................................................................................. Hercostomus falcilis sp. nov.

In the key to Chinese species ( Yang et al. 2011), the new species runs to Hercostomus ulrichi Yang , but can be distinguished from the latter by the black postocular setae.

Figures

FIGURE 2. Hercostomus falcilis sp. nov. (A) hypopygium, left lateral view; (B) hypopygium, ventral view; (C) antenna, lateral view.