Tethina

Munari, Lorenzo, 2016, The Canacidae of the Arabian Peninsula (Diptera: Brachycera: Carnoidea), Zootaxa 4092 (4), pp. 489-517 : 501

The Tethina species of the alboguttata -group

This taxonomically very difficult group of species is characterised mainly by the depigmented crossveins of the wing, which are milky white, sometimes with a white halo surrounding them (not present in the species of the Arabian Peninsula); gena generally evenly microtomentose, sometimes with a faint longitudinal subshiny stripe; male terminalia with surstylus bearing an obvious mesal lobe (visible in posterior view); female cerci with many stout, upward curved, spine-like setae (pseudacanthophorites, according to Freidberg and Beschovski, 1996). Specimens from the Arabian Peninsula are also characterised by a pale whitish to grey microtomentum that generally coats the body cuticle. Munari (2010) pointed out a consistent, peculiar character occurring in most of the Arabian species of Tethina of the alboguttata -group, that is, a characteristic black macula clearly visible at the base of wing vein R1 (fig. 30). Except for Tethina spinigera Munari, 2008 a and T. callosirostris Munari, 2008 a, in which this character does not occur or is poorly obvious, in all the other species belonging to this group (mostly Macaronesian-Mediterranean species) this peculiarity is lacking. As for T. spinigera (a species with no obvious black macula on R1), it exhibits an interesting and unique chaetotactic pattern of the epandrium, consisting of short, stout spinulae rather than long setae, that allows its taxonomic placement as a possible sister species of the remaining Arabian species of the Tethina alboguttata -group. On the base of vein R1, T. callosirostris shows instead a simple, transverse, fine, black line, like that occurring in some Mediterranean species. The unique occurrence of a black macula (an apomorphic character state) in the species from the Arabian Peninsula would indicate this region to be a possible, common centre of speciation.

The species listed below are distinguished from congeners of the alboguttata -group by the combination of diagnostic characters specified in the following treatment.