Sphegina (Asiosphegina) trichaeta, Hippa, Heikki, Steenis, Jeroen Van & Mutin, Valeri A., 2015

Hippa, Heikki, Steenis, Jeroen Van & Mutin, Valeri A., 2015, The genus Sphegina Meigen (Diptera, Syrphidae) in a biodiversity hotspot: the thirty-six sympatric species in Kambaiti, Myanmar, Zootaxa 3954 (1), pp. 1-67 : 25-27

Sphegina (Asiosphegina) trichaeta sp. n.

Figs 13 A–D

MALE. Body length 7.5–8.5 mm, wing length 6.5–7.0 mm. Head. Face moderately concave and weakly projected antero-ventrally; frontal prominence weakly developed (similar to Fig. 1F). Width of vertex at anterior ocellus less than 1/4 of the width of head [1:4.5]; depth of occipital fossa ca. 1/4 of the width of an eye in dorsal view [1:3.7]. Width of face: width of head 1:4.5. Face black, pale pollinose, the pollinosity weaker ventrally than dorsally. Gena shiny black or brown. Frons dull black, lunula shiny brown, posteriorly from the frontal prominence with a narrow pale pollinose fascia, the pile erect, short, yellow or reddish; vertex dull black. Occiput dull black. Antenna brown; basoflagellomere paler than scapus and pedicellus, red baso-ventrally; arista pilose. Thorax. Black, more or less densely pale pollinose, postalar callus brown; the pile of scutum short and adpressed, pale, posteriorly intermixed with some longer erect pile; scutellum short-trapezoidal, pile pale, with a pair of widely

separated long usually pale setae at apical margin. Wing. Hyaline, stigma yellowish. Legs. Proleg yellow, brownish on large part of femur, medially on tibia and on tarsomeres 4 and 5. Mesoleg with coxa and trochanter yellow; femur brown, the basal 1/6 and the apex yellow; tibia yellow with a more or less wide brownish annulus near the middle; tarsus yellow, tarsomeres 4 and 5 brown. Metaleg: coxa brown; trochanter simple, yellow; femur uniformly thickened on the basal part, black, yellow on basal 1/4, where with antero-ventral patch of very small black and yellow setulae near base; tibia with an apicoventral tooth, brown, yellow on basal 1/4 and on an annulus on the apical 1/2; tarsus black. Abdomen. Length ratio of tergites I, II, III and IV 1:2.9:1.7:1.3. Colour of tergites black, anterior 1/3 of tergite III yellow, pile pale, short and adpressed, becoming longer laterally; tergite I at lateral margin with 2 strong black setae with 1 rather thin yellow seta in front; sternite IV ( Fig. 13 A) black, pile pale, a few longer erect individual hairs posteriorly, the strong setae and bristles black or dark brown; sternites VI and VII simple, black, the pile long, erect and pale; sternite VIII black, the pile rather short and pale, more dense anteriorly. Genitalia, Figs 13 B–D. Note the strongly asymmetrical surstyli, slightly asymmetrical superior lobes, the medial lobe at the base of the dorsal lobe of the left side surstylus and the long aedeagal lobe. FEMALE. Body length 6.7– 8.1 mm, wing length 5.4–7.0 mm. Similar to male except for the normal sexual dimorphism. Abdomen mainly black except dorsally indistinct reddish-brown anterior macula on tergite III, and tergite V entirely orange-brown; length ratio of tergites I, II, III and IV 1:2.6:2.3:1.9; tergite I with 2 clearly separated strong black setae on posterior 1/2 laterally; ratio of length:width of tergites III and IV 1:1.1 and 1:1.3; tergite V elongate with medial transversal groove, with long pale erect pile; sternite IV trapezoid, about 2 times as long as broad, with arcuate posterior margin, brown, pile short, pale; sternite V semirectangular, rounded posteriorly, with very long pale pile posteriorly.

Type material. HOLOTYPE. ♂, N.E. Burma, Kambaiti, 7000 ft., 7.v.1934 R. Malaise ( BMNH). PARATYPES. 2♀ with same data ( BMNH, NBC); 1♂ with same data except 23.v. ( SMNH); 1♂ with same data except 14.v. ( SMNH); 3♀ with same data except 2000 m, 4.vi. ( SMNH, NBC); 1♂ and 1♀ with same data except 11.vi. ( SMNH, NBC); 2♂ with same data except 12–17.vi. ( SMNH, NBC).

Etymology. The name is composed of, and Latinized, from the Greek words treis, three, and chaite, seta, referring to the three strong setae on male sternite IV.

Discussion. Sphegina trichaeta belongs to a group of species in which the male tergite IV posteriorly bears strong spinose setae in an asymmetrical pattern and which have the left side dorsal lobe of surstylus broader that the right side one (see also under S. crassispina above). The other similar species in this respect are S. radula , S. raduloides and S. subradula . In addition to the characters mentioned in the key, S. trichaeta differs from the three latter e.g. by male sternite IV which has a group of three long setae on the left side, about half the width of the sternite and greatly deviating from the other setae, the others have two or three short setae, one fifth of the width of sternite or shorter and not greatly deviating from the other setae. Also the male genitalia of all the four species are very similar. S. trichaeta is distinguished from S. subradula e.g. by a much narrower dorsal lobe on the left side surstylus, from S. radula by having the ventral margin of the superior lobe straight (not with an angulate lobe) and by having a much larger aedeagal lobe and from S. raduloides by having the dorsal margin of the left side superior lobe smoothly curved, not angulate, and by having posteriorly one-lobed, not bilobed superior lobe.

Figures

FIGURE 13. Sphegina (Asiosphegina) trichaeta sp. n. (holotype). A. Posterior part of sternite IV, ventral view; the unmodified pilosity omitted. B. Genitalia, lateral view. C. Left surstylus, lateral view. D. Left superior lobe, lateral view. Scale 0.5 mm.