argenteus group

Diagnosis

Katepisternum with a posterodorsal and a weak (composed of a few setae only) posteroventral pile patch, without setae between them. The bare flat posterior margin of tergite 1 (almost) entirely without microtrichia. Base of wing entirely microtrichiose or at most with small bare areas in cells br, bm, or cup. Anepisternal setae saw-like. Protarsomere 1 anterodorsally with a line of minute black spinules (yellow in M. argentimaculatus sp. nov. and M. tabanoides sp. nov.) between the yellow trichia.

♂: sternite 4 with flat caudal lobes, entirely microtrichiose. Genital pouch less than half as wide as abdominal segment 4 at anterior margin. Posterior surstyle lobe directed medially, its apex forming a strong twisted hook (Fig. 13A:y). Median surstyle lobe setose along ventral margin on full length, on median surface extensively covered by microtrichia and posteriorly with a small inner accessory lobe pointing medially (Fig. 13D:x). Cerci (Fig. 10:z) with blunt apex, ventral surface membraneous and without setae. Subepandrial sclerite strongly curved (in lateral view, Fig. 10:w), and its anterior end sclerotized at the sides only, sclerotized but translucent in the middle, posterior part with a strongly trichiose pillow-like structure, which is densely furnished by unusually long and thick microtrichia (Fig. 13C, D:z), otherwise bare. Hypandrium (Fig. 12:A–J) with a moderately wide base (in ventral view), without ‘shoulders’ between wide base and narrower distal half, apex distinctly produced beyond ctenidium and pointed. Ejaculatory apodeme small. The male terminalia of all included species are very similar (Figs 10–12), the significance of the observed small differences between species needs to be proved by more material.

♀: tergite 5 and sternite 5 with posteriorly directed setae, ovipositor with moderately thick setae, without tooth.

The argenteus group can be subdivided into two subgroups, at least the first being monophyletic. A full description is given for M. argenteus comb. nov., which is the only fairly common species of this group (all others being rare or known from singletons only). The descriptions of the remaining species focus on the differences to M. argenteus .