Sphegina (Asiosphegina) bidens, 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 : 39-41

Sphegina (Asiosphegina) bidens sp. n.

Figs 2 F, 23A–D

MALE. Body length 6.5–7.9 mm, wing length 5.7–6.5 mm. Head. Face strongly concave, moderately projected antero-ventrally; frontal prominence moderately developed (somewhat similar to Figs 1J, K). Width of vertex at anterior ocellus:width of head 1:3.6; depth of occipital concavity more than 1/3 of the width of an eye in dorsal view. Width of face:width of head 1:3.9. Face brownish, with dense pale pollinosity dorsally, ventral 1/2 yellow, weakly pollinose. Gena shiny yellow. Frons and vertex weakly shiny dark brown, with a semitriangular palepollinose macula laterally just posteriorly from the shiny frontal prominence, the pile short, erect and pale. Lunula brownish. Frontal prominence with shallow medial groove. Occiput dull black. Antenna entirely yellow; basoflagellomere oval, ratio of length:width 1:0.8; arista pilose. Thorax. Colour dull black or mainly brown laterally, postpronotum and postalar callus brown, in some specimens with pleura obscurely paler under the wing base; scutum anteriorly with a submedial macula of pale pollinosity which continues posteriorly as a narrow, obscure, pale-pollinose fascia, the pile reddish, rather long, dense and semi-erect; the sparse pile on pleura erect and pale; scutellum trapezoid, the pile similar to that on the posterior part of scutum with a pair of very thin, not longer than scutellum, pale setae at apical margin. Wing, Fig. 2 F. Hyalinous, stigma yellowish, transversal veins infuscated. Legs. Pro- and mesoleg yellow, sometimes tarsomere 5 brownish. Metaleg: coxa brownish; trochanter simple, brownish; femur yellow, the apex and a ventrally interrupted annulus on the basal 1/2 brownish; tibia without apico-ventral tooth, brownish except the basal 1/4 and a broad annulus on the apical 1/2 yellow; tarsus dark brown. Abdomen. Length ratio of tergites I, II, III and IV 1:3.5:1.9:1.3. Tergites shiny black or brown, the anterior 1/4 of tergite III yellow, the pile of tergites mainly dark medially, short and adpressed, becoming paler towards tergite IV which has nearly entirely pale pile; tergite I with 3 strong, dark, widely separated setae at lateral margin, in some specimens a fourth seta present posteriorly and positioned dorsally from the third one; sternite IV ( Fig. 23 A) nearly symmetrical, brown, the pile pale; sternites VI–VIII simple, black, the pile pale. Genitalia, Figs 23 B– D. Note the symmetrical surstyli and superior lobes and the apically broadened aedeagal lobes. FEMALE. Body length 5.9–6.8 mm, wing length 5.2–5.9 mm. Similar to male except for the normal sexual dimorphism. Length ratio of tergites I, II, III and IV 1:2.9:2.1:1.4; tergite III with an oval brown-yellow macula anteriorly; tergite I with 1 or 2 strong yellow setae antero-laterally; ratio of length:width of tergites III and IV 1:1.3 and 1:1.9; sternite IV trapezoidal, as long as or slightly longer than broad, brown; sternite V rectangular, longer than broad.

Type material. HOLOTYPE. ♂, N.E. Burma, Kambaiti, 1800 m, 23.vi.1934, R. Malaise ( SMNH). PARATYPES. 2♂ with same data as holotype except 2000 m., 25.v. ( SMNH, NBC); 2♂ with same data except 2000 m., 29.v. ( SMNH, NBC); 1♂ with same data except 2000 m., 4.vi. ( SMNH); 2♀ with same data except 2000 m., 12–17.vi. ( SMNH, NBC); 1♀ with same data except 7000 ft., 16.v. ( SMNH); 1♀ with same data except 7000 ft., 28.v. ( SMNH); 1♂ with same data except 7000 ft., 4.vi. and Sphegina tristriata Brun det. v. Doesburg ( SMNH).

Etymology. The name is Latin, bidens , two-toothed, referring to the two-toothed postero-dorsal part of the male superior lobe.

Discussion. Sphegina bidens resembles S. forficata , S. crucivena , S. nasuta and S. simplex , but is not closely similar to any of them. Except for the characters mentioned in the key it differs from all by the male genitalia, especially by having a bifid apex of the superior lobe and apically expanded aedeagal lobe. S. bidens is also similar to S. orientalis but the latter differs by having dark (not pale) pro- and metatarsus, simple (not apically bifid) superior lobe and by very narrow aedeagal lobe, similar to that of S. nasuta , which is not apically expanded.

According to Brunetti’s (1913, 1923) description, Sphegina tristriata Brunetti, 1913 seems similar to S. orientalis and other species resembling it ( S. nasuta and S. simplex ). The description is based on a female and the identity of the species remains obscure. Based on the brownish-yellow thorax with medial and submedial dark vittae S. tristriata mostly recalls S. bidens but differs by having a yellow fascia anteriorly on tergite III (an oval brown-yellow macula in S. bidens ).

Figures

FIGURE 2. Wing. A. Sphegina (Sphegina) uncinata sp. n. (paratype). B. S. (Asiosphegina) furva sp. n. (paratype). C. S. (A.) nasuta sp. n. (paratype). D. S. (A.) crucivena sp. n. (paratype). E. S. (A.) crassispina sp. n. (paratype). F. S. (A.) bidens sp. n. (paratype). G. S. (A.) carinata sp. n. (paratype). H. S. (A.) index sp. n. (paratype). I. S. (A.) simplex sp. n. (paratype). Scale 0.5 mm.

FIGURE 23. Sphegina (Asiosphegina) bidens sp. n. (holotype). A. Posterior part of sternite IV, ventral view. B. Left surstylus, lateral view. C. Left superior lobe, lateral view. D. Genitalia, lateral view. Scale 0.5 mm.