Key to genera of Usiini Becker

1. Disc of mesonotum largely obscured by dust and hairs on abdomen pale (white to yellow). If with shining mesonotal vittae (which, in U. loewi, occasionally coalesce such that disc is largely devoid of dust) abdomen with yellow apical margins, disc of tergites matt, laterally densely grey-dusted [all holoptic species and all but one with yellow apical margins to tergites belong here]................................................................................................ 2 - Either disc of mesonotum shining and undusted and tergites shining largely undusted or abdominal hairs black (if with yellow apical margins to tergites, U. transcaspica, tergites, except first, shining, undusted, even laterally)...................... 3

2. Anal lobe well developed, at least as wide as anal cell; entirely pale-haired species (white to yellow). Grey, brown or blackish dusted species, abdomen matt usually with pale apical margins to tergites. Furca variable, often heavily sclerotised........................................................................................... Parageron Paramonov

- Anal lobe narrow, linear in ♂, almost linear in ♀, narrower than anal cell; with some dark brown hairs on mesonotum and scutellum (these can fade). Olive-grey and brown-dusted but rather thinly so subshining (somewhat variable). Epandrium with shining patches. Furca V-shaped folded over at distinct ‘seam’. Genitalia (see Gibbs 2011 pl I).............................................................................................. Usia martini François (see Gibbs 2011)

3. All hairs on head, thorax and abdomen clearly black............................................................................................. Usia subgenus Micrusia Evenhuis and Usia versicolor (Fabricius) (see Gibbs 2011)

- At least hairs on down-curved lateral margins of tergites pale yellowish (only one species with dark vestiture, U. aeneoides, in which the dark mesonotal hairs are very short spicules)............................................. Usia Latreille