Hercostomus nigricollaris 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 : 70-72

Hercostomus nigricollaris Negrobov, Kumazawa & Tago sp. nov.

( Figs 4 A–E, 8D)

Hercostomus sp. № 11t. Tago, 2012: 7.

Type material. HOLOTYPE Ƌ, labeled: Japan, Saitama pref., Irikawa, Ootaki, Chichibu City , 6.vii.2011, leg. T. Tago ( OMNH) . PARATYPES: 4 Ƌ, same data as holotype (2 Ƌ OMNH, 2 Ƌ VSU) .

Description. Male. Head with frons dull with dense silvery-white pollinosity. Face narrow with dense white pollinosity with greenish tinge, without hairs, not reaching lower eye margin, middle part narrower than postpedicel width. Proboscis and palpus yellow, palpus with 1 black seta and black hairs. Antenna ( Fig. 4 C) black. Postpedicel longer than wide. Stylus placed on dorsal side of postpedicel, with short hairs. Ratio of 1st and 2nd segments of stylus: 3.6: 5.2. Ratio of postpedicel length to width and stylus length: 3.9: 2.4: 8.7. Postocular setae black. Thorax dark-green, humeral tubercle yellow, bright, without pollinosity. Pleura yellow, with dark spot on pteropleuron. Propleuron with 1 black seta below, with yellow hairs above. Scutellum bare above, with 2 strong black lateral setae and small marginal hairs. Legs yellow, apical part of mid and hind tarsi darkened. Segments of tarsi simple, not widened. Femora without long hairs below. Fore femur without preapical setae. Fore tibia without long apicoventral seta, with 1 short anterodorsal and 2 short posterodorsal setae, with row of small anteroventral setae in apical 2/3. Segments of fore tarsus without hairs. Ratio of length of fore tibia and tarsomeres (from 1st to 5th): 5.4: 3.4: 1.9: 1.4: 1.0: 0.8. Mid femur with 1 long preapical outer seta and 1–2 preapical inner hairs. Mid tibia with 3 long anterodorsal, 2 posterodorsal and 1 anteroventral setae. 1st segment of mid tarsus without setae. Ratio of length of mid tibia and tarsomeres (from 1st to 5th): 8.2: 4.2: 3.2: 1.6: 1.4: 1.0. Hind coxa with 1 black outer seta. Hind femur with 1 preapical outer seta. Hind tibia thickened apically, with 4 long anterodorsal, 4 long posterodorsal and 5–6 short anteroventral setae. Ratio of length of hind tibia and tarsomeres (from 1st to 5th): 9.7: 2.8: 3.8: 2.3: 1.5: 1.2. Tarsomere 1 of hind tarsus with 3–4 small ventral setae, other segments of hind tarsus with small hairs. 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: 0.8. R4+5 and M1+2 convergent apically. Ratio of m-cu to apical part of M3+4—1.5: 1.9. Anal angle obtuse. Calypter yellow with black cilia. Halter yellow. Abdomen bright green, with black setae and hairs. Abdominal segment 1 at base and abdominal sternites yellow, abdominal tergites 2–4 with yellow spots laterally. Abdominal segment 8 brown. Epandrium ( Figs 4 A, B) brown, oval, longer than wide. Surstylus black. Cercus shorter than epandrium, widened oval apically, with long black hairs, brown, yellow at base. Female. Unknown. Length (mm): body: 2.3–2.4 mm, wing: 2.4–2.6.

Etymology. The species is named for the black postocular setae.

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 acutangulatus Yang & Saigusa, 1999 , but can be distinguished from the latter by the morphology of hypopygium ( Figs 4 A, B) and following characters:

- Pleura mostly metallic green, metapleuron yellow. Abdominal segments 1–2 yellow laterally....................................................................................... Hercostomus acutangulatus Yang & Saigusa, 1999 - Pleura yellow. Abdominal segments 1–4 yellow laterally........................... Hercostomus nigricollaris sp. nov.

In the key to Chinese species ( Yang et al. 2011), the new species runs to Hercostomus ulrichi Yang, 1996 , but can be distinguished from the latter by following characters:

- Cercus short, approximately 2 times shorter than epandrial processes. Epandrial processes long oval, with long hairs and black seta............................................................................ Hercostomus ulrichi Yang - Cercus long, longer than epandrial processes Epandrial processes short............... Hercostomus nigricollaris sp. nov.

Figures

FIGURE 4. Hercostomus nigricollaris sp. nov. (A) hypopygium, left lateral view; (B) hypopygium, ventral view; (C) antenna, lateral view; (D) right cercus, ventral view; (E) surstylus, postgonite, left lateral view.