Megaselia vannusetarum Disney, 2006, sp. nov.

Megaselia vannusetarum sp. nov.

(Figs 34, 35)

In the keys of Beyer (1965) most specimens of this species run to couplet 3, lead 1, on page 53, to M. tenuicosta Beyer, which is immediately distinguished by its brown palps and dusky wings. Some specimens, with the costal index <0.44, run to couplet 3, lead 2, on page 56, to M. lilliput Beyer. It thus also closely resembles the omitted M. mera, M. pseudomera (see above) and M. vitiomera (see below) and differs in the same features from Beyer’s species, except it has the haltere knobs coloured as in M. mera. The males are instantly distinguished by the conspicuously modified bristles at the rear of the venter of abdominal segment 6.

Etymology

The name derives from the Latin for winnowing fan and bristles, and refers to the modified bristles at the rear of the venter of abdominal segment 6 of the male.

Male

Head very similar to M. pseudomera except labrum is only about half as wide as postpedicels, which are brown, and labella closely resemble those of M. mera (Fig. 20).

Thorax brown. Mesopleuron bare. Two notopleural bristles and no cleft in front of these. Scutellum with an anterior pair of hairs (much shorter than hairs at rear of scutum) and a posterior pair of bristles. Abdominal tergites brown with the hairs at rear of T6 longer than rest (Fig. 34). Venter brownish grey, and with hairs below segments 3–6, but the four most ventral ones on 6 are modified into fan­shaped structures (Figs 34 and 35). Hypopygium brown, except for straw yellow vestigial lobes of hypandrium and lightly tinged brown anal tube, and as Fig. 34. With two rectal papillae. Legs straw yellow but at least outer half of hind femur increasingly brown towards tip, the dorsal edge of hind tibia brown and there is a brown patch on the mid coxa. Fore tarsus with posterodorsal hair palisade on segments 1–5, and 4 and 5 are subequal in length. Dorsal hair palisade of mid tibia extends almost three quarters of its length. Some hairs below basal half of hind femur clearly longer than those of anteroventral row of outer half. Hind tibia with 9–12 differentiated posterodorsal hairs. Spinules of apical combs simple. Wings 0.9–1.2 mm long. Costal index 0.40–0.45. Vein 3 unforked. Costal ratios 1.3–1.6: 1. Costal cilia (of section 2) 0.05–0.07 mm long. Hair at base of vein 3 shorter than costal cilia. With two axillary bristles, the outer being longer than costal cilia. Sc not reaching R1. Costa with a slight thickening near middle of section 1. Veins yellowish grey, but 7 very pale. Membrane very lightly tinged grey. Haltere with brownish yellow knob and brown stem.

Material

HOLOTYPE male, Seychelles, Silhouette Island, La Passee above mausoleum, 1–4 July 2000, J. Gerlach (CUMZ, 8­125); Paratypes, 3 males as holotype; 1 male, Bird island, 16 September 2003, J. Gerlach (CUMZ, 8­149); 1 male, Lantana, Lantana North, 30 July – 1 August 2000, J. Gerlach (CUMZ, 124).