Two new species of Amblypsilopus Bigot with a key to species from Taiwan (Diptera, Dolichopodidae)

Abstract The following two new species of the genus Amblypsilopus Bigot from Taiwan are described: Amblypsilopus flavellus sp. n. and Amblypsilopus ventralis sp. n. One species, Amblypsilopus crassatus Yang, 1997, is newly reported from Taiwan. A key to the species of the genus from Taiwan is given.


Introduction
The genus Amblypsilopus Bigot is a large genus in the subfamily Sciapodinae with 275 known species from the world (Bickel 1994;Yang et al. 2006). There are 45 known species from China, of which 8 species occur in Taiwan (Yang et al. 2011). This genus is characterized by the following features: body usually appearing delicate with long thin legs; arista usually dorsal, shorter than head width; crossvein m-cu straight; male vertical seta reduced (Bickel 1994;Yang et al. 2011). The major references dealing with the Oriental species of Amblypsilopus are Becker (1922), Bickel (1994), and Yang et al. (2011). The Chinese species were reviewed by Yang et al. (2011). Here three species including two new species are added to the fauna of Taiwan. A key to the species of the genus from Taiwan is given.
Description. Male. Body length 4.5 mm, wing length 4.0 mm. Head brightly metallic green with pale grey pollen. Hairs and bristles on head pale yellow; frons with 1 pale curved and slightly thick hair on posterolateral slope; 1 pvt at end of postocular line. Ocellar tubercle with 2 long strong oc and 2 posterior hairs. Antenna yellow; pedicel with circlet of short blackish apical bristles except 1 dorsal bristle and 1 ventral bristle relatively long; first flagellomere short triangular, nearly as long as wide; arista [broken apically] apical, blackish. Proboscis yellow with pale yellow hairs; palpus yellow with pale hairs and 2 brownish yellow bristles.
Abdomen pale metallic green with thin pollen except segments 1-4 dark yellow or yellow with posterior margins of tergites 1-4 brown or dark brown. Hairs and bristles on abdomen black. Male genitalia (Fig. 1): Epandrium longer than wide in lateral view; epandrial lobe short, obtuse. Surstylus finger-like, slightly bent. Cercus dark yellow, shorter than epandrium, finger-like, basally slightly curved. Hypandrium apically nearly straight, with lateral arm rather thick near base.
Remarks. This species belongs to Amblypsilopus pallidicornis group. It is similar to C. flavicercus Zhu & Yang from Hainan of China, but can be separated from it by the antenna entirely yellow, male cercus shorter than the epandrium and distinctly curved basally, and surstylus long and distinctly bent. In C. flavicercus, the antennal scape and flagellum are brownish at tip, male cercus is as long as the epandrium and nearly straight, and the surstylus is short and nearly straight (Yang et al. 2011).
Etymology. The specific name refers to the yellow antenna.
Thorax brightly metallic green with pale grey pollen. Hairs and bristles on thorax black; 5 long strong dc; 3-4 very short, paired acr present before anteriormost dc; h indistinct, 1 ih, 1 ph, su absent, 2 sa, 1 psa, 2 npl; scutellum with two pairs of sc, basal pair very short and hair-like (about 1/5 of apical pair). Legs yellow except mid and hind coxae brown with yellow apex and tarsi dark brown from tip of fore tarsomere 1 onward. Hairs and bristles on legs black except coxae with pale yellow hairs and bristles. Fore coxa with 3 bristles, hind coxa with 1 brownish yellow exterior bristle. Fore femur thickened with two rows of v on basal 2/3 and narrowed on apical 1/3. Fore tibia ventrally slightly swollen at base, with 4 pv and one row of short dense av hairs, without distinct d; apically with 1 pd and 1 p. Mid tibia with 3 strong ad and 3 weak pd; apically with 1 ad and 1 av. Hind tibia with 4 pd and 2-3 weak pv at middle; apically with 1 ad and 1 av. Hind tarsomere 1 with 1 v at extreme base. Relative length ratio of tibiae and tarsomeres: LI 1.9 : 1.7 : 0.7 : 0.5 : 0.3 : 0.2; LII 3.2 : 2.4 : 0.9 : 0.6 : 0.2 : 0.25; LIII 4.0 : 1.5 : 1.1 : 0.6 : 0.4 : 0.2. Wing nearly hyaline, veins dark brown. Vein M 1 basally curved nearly at a right angle. Crossvein m-cu straight, CuAx ratio 1.3. Squama yellow with dark brown margin and with pale hairs. Halter dark yellow.
Abdomen metallic green with thin pollen except venter and hypopygium pale metallic green. Hairs and bristles on abdomen black except those on lateral portion of tergite 1 pale yellow. Male genitalia (Fig. 2): Epandrium wider than long in lateral view; epandrial lobe indistinct. Surstylus slightly thick, apically shallowly furcated. Cercus about two times as long as epandrium, long finger-like, basally thick with subtriangular ventral process. Hypandrium distinctly bent apically, with thin lateral arm.
Remarks. This species is somewhat similar to A. basalis Yang from Southern China, but can be separated from it by the antenna black, and male cercus as long as the epandrium, with the large ventral process at base. In A. basalis, the antenna is yellow, and male cercus is about two times as long as the epandrium and has the small ventral process at base (Yang 1997;Yang et al. 2011).
Etymology. The specific name refers to the fore femur with two rows of short v.
thanked for providing useful comments on an earlier draft of this paper.