Usia versicolor (Fabricius, 1787)

Gibbs, David, 2011, 2960, Zootaxa 2960, pp. 1-77 : 73

Usia versicolor (Fabricius, 1787)

Diagnosis. From all other members of the Usiini by a combination of entirely black vestiture and the presence conspicuous suberect black bristles on mid-tibia apicoventrally. Mesonotum smooth and unwrinkled, in the male the disc densely dusted so as to obscure the ground colour, female uniformly thinly brown dusted so ground colour still apparent. Labium in males distinctly hairy both ventrally and laterally, especially in the typical form ( Micrusia has no more than microscopic setae on labium while a few typical Usia possess short setae ventrally). Females lack these long hairs on the labium, possessing short setae along much of its length ventrally, decidedly more conspicuous than in Micrusia . The hairs on U. versicolor , especially in males, are more bristle-like, stiffer looking and parallel-sided, coming to an abrupt point. In Micrusia vestiture hair-like, tapering along their length to a fine point.

The male genitalia are not particularly large but fall within the range seen in Micrusia . Epandrium, gonocoxite and epiphallus show no similarity with any other species within Micrusia or typical Usia . The gonostyli are bifurcate quite unlike any Micrusia and not very similar to any typical Usia .

Female genitalia similar to many species of both Micrusia and typical Usia , furca simple V-shaped, vaginal plate very small and translucent. Apical sternite relatively flat, rather different from most Micrusia .

History and affiliations. One of the earliest species of Usiini to be named and treated with the other blackhaired species by Becker (1906), Engel (1932) and Paramonov (1950). Evenhuis (1990) placed U. versicolor in his new subgenus Micrusia and this was followed in (Evenhuis & Greathead 1999). The genitalia were first figured by Engel (1932) with external lateral and ventral views of the male genitalia (his Textfig. 28). Theodor (1983) was the first to publish detailed illustrations of the macerated male genitalia (his Figs. 143–145). Both male and female genitalia were illustrated by Evenhuis (1990) (his Fig. 29 and 30 although the male genitalia are mislabelled Usia (Micrusia) forcipata ).

As set out in the diagnosis section above, U. versicolor has some unique features that set it apart from other members of the genus. Males are strikingly colourful insects with dense olive brown and rufous dusting quite different to the dusting seen on other Usia . Probably of particular systematic importance is the group of short, black spicules on the mid-tibia apicoventrally not seen in any other species of the subfamily. The male genitalia also do not fit with any other species in either Micrusia or Usia sensu stricto suggesting a separate linage. However, females are superficially very like some species of Micrusia and the genitalia suggest that U. versicolor is perhaps closer to Micrusia than to Usia sensu stricto. This species is probably a very early radiation from the base of the Micrusia linage that has spread around the western Mediterranean without speciating.