Sphegina (Asiosphegina) gigas, 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 : 22-24

Sphegina (Asiosphegina) gigas sp. n.

Figs 1J, M, 3D, 4B, 11A–E

MALE. Body length 9.0– 9.5 mm, wing length 7.5–7.8 mm. Head (Figs 1J, M). Face moderately concave and moderately projected antero-ventrally; frontal prominence weakly developed. Width of vertex at anterior ocellus a little more than 1/4 width of head; the depth of occipital fossa ca. 1/3 of the width of an eye in dorsal view. Width of face: width of head 1:4. Face black, pale pollinose. Gena shiny black. Frons and vertex black, semi-shiny; lunula shiny brown. Occiput dull black. Antenna entirely dark, dark brown to blackish; arista distinctly pilose. Thorax. Colour black, weakly pollinose, semi-shiny; postalar callus brownish; the pile of scutum short, adpressed and reddish; scutellum transverse [ratio of length:width 1:2.7], the pile longer and more erect than that on scutum; a pair of long, thin, black setae at apical margin. Wing. Hyaline, stigma yellowish. Cross vein dm-cu oblique to vein M1+2, straight; vein M1 straight. Legs. Pro- and mesoleg yellow except tarsomere 3 usually darkened, tarsomeres 4 and 5 black; metaleg (similar to Fig. 3 D): coxa brownish; trochanter yellow, simple; femur black, the basal 1/4 yellow, a prominent dark seta antero-dorsally near the apex, with a few black setae ventrally on the pale basal part; tibia without an apico-ventral tooth, black, the basal part paler brownish, the apical 1/2 with a broad yellow annulus; tarsus blackish entirely. Abdomen. Length ratio of tergites I, II, III and IV 1:4.0:2.2:1.2; colour of tergites shiny black, the anterior 1/4 of tergite III yellow, pile of tergites short and adpressed, pale, becoming longer towards the lateral margin; tergite I with 3 well separated strong, black setae at lateral margin ( Fig. 4 B); sternite IV ( Figs 11 A, B) brown; pile, the strong setae and bristles black; sternite VI ( Fig. 11 A) with a long finger-like process, covered by long pale pile, black; sternites VII and VIII simple, black, the pile pale, pile on sternite VIII shorter than on sternite VII. Genitalia, Figs 11 C–E. Note the strong asymmetry of the surstyli and the superior lobes and the short finger-like process subbasally on the medial side of the dorsal lobe of surstylus. FEMALE. Body length 9.3 mm, wing length 8.2 mm. Similar to male except for the normal sexual dimorphism. Abdomen similar to male, but tergites III and IV broader, ratio of length:width of tergite respectively 1:1.1 and 1:1.9; length ratio of tergites I, II, III and IV 1:3.4:2.6:1.1; tergites I–IV black, mainly with pale erect adpressed pile; tergites V and VI brown, both with long pale pile; sternite IV trapezoid, slightly narrowed anteriorly, brown, pile pale and adpressed (ratio of length:width 2.5:1); sternite V semitriangular, rounded posteriorly, yellow with very long pale pile on posterior part and on antero-medial semitriangular depression.

Type material. HOLOTYPE. ♂, N.E. Burma, Kambaiti, 2000 m., 12–17.vi.1934, R. Malaise ( SMNH). PARATYPES. 1♀ with same data as holotype ( SMNH); 1♀ with same data except 1800 m., 28.vi. ( NBC); 1♂ with same data except 7000 ft., 26.v. ( NBC); 1♂ with same data except 7000 ft., 28.v. (strongly damaged, in SMNH); 1♀ with same data except 7000 ft., 12–17.vi. ( BMNH).

Etymology. The name is Greek, gigas , giant, referring to the large size of the fly.

Discussion. Sphegina gigas is similar to S. carinata , S. crassispina , S. index , S. malaisei and S. trispina . Except for the characters appearing in the key, it differs from the first four species by having black setulae basoventrally on the metafemur; from S. trispina it differs greatly in the armature of the left side of male sternite IV in which there is a transverse row of strong setae diminishing in length towards the medial line (three long and ca. four very short ones in S. trispina ). The male genitalia of S. gigas are very similar to those of S. trispina , the superior lobes especially on the right side being almost identical. S. gigas differs by narrower surstylus and by having the small lobe basomedially on the surstylus more ventral in position and directed ventrally, not posteriorly as in S. trispina . In S. gigas the finger-like process on male sternite VI is larger than in any other of the studied species. It is probably homological with the tubercle in those cases where there are two processes, a finger-like one and a tubercle-like one as in S. carinata , S. crassispina , S. index and S. malaisei . S. gigas resembles S. bispinosa and S. hansoni , (see also under S. carinata ) but differs from both by the hyaline wing (in S. bispinosa and S. hansoni wing with infuscated pattern).

According to its original description ( Shiraki 1930), S. nigerrima Shiraki is similar to S. gigas , S. malaisei and S. trispina but differs by having submedial pollinose vittae on mesonotum and by lacking a subapical yellow annulus on metatibia.

Figures

FIGURE 3. Metaleg, prolateral view (A, D female, B, C, E male). A. Sphegina (Asiosphegina) bilobata sp. n. (paratype). B. S. (A.) forceps sp. n. (paratype). C. S. (A.) minuta sp. n. (paratype). D. S. (A.) gigas sp. n. (paratype). E. S. (A.) carinata sp. n. (paratype). Scale 1.0 mm.

FIGURE 4. Tergite I (A – E), lateral view, abdomen (F, G, H), dorsal view. A, F. Sphegina (Asiosphegina) simplex sp. n. (paratype). B. S. (A.) gigas sp. n. (paratype). C. S. (A.) radula sp. n. (paratype). D, H. S. (A.) crassispina sp. n. (paratype). E, G. S. (A.) parvula sp. n. (paratype). Scale 0.5 mm for A – E, 1 mm for F, G, H.

FIGURE 11. Sphegina (Asiosphegina) gigas sp. n. (A, B, paratype, C, D, E holotype). A. Posterior part of abdomen, lateral view; the unmodified pilosity omitted. B. Sternite IV, ventral view; the unmodified pilosity omitted. C. Genitalia, lateral view. D. Left surstylus, lateral view. E. Left superior lobe, lateral view. Scale 0.5 mm.