Therevidae

Key to genera of Therevidae known in British Columbia, Yukon, and Alaska This key is adapted from Irwin & Lyneborg (1981), Webb & Irwin (1999), and Webb & Metz (2003) using non-genitalic characters. A few couplets require the differentiation of the sexes. The compound eyes of male therevids in the region treated usually touch dorsally, although in Tabuda and Dichoglena they are narrowly separate, no farther apart than the width of the ocellar tubercle. They are much more widely separate in all females. Females have distinctive acanthophorite spines at the tip of the abdomen; these are short, truncate, and arranged in two fanshaped groups. In the male genitalia, the dorsal, plate-like epandrium is usually apically bifid with the lateral apices pointed and enclosing the often-prominent cerci. Genitalia, especially in males, is sometimes difficult to see because of dense setae. 1 Midcoxae with long hairs on posterior surface.............................................................. 2 - Midcoxae bare on posterior surface, or with only a few appressed hairs......................................... 10 2 Prosternum with hairs in and around central depression....................................................... 3 - Central depression of prosternum bare.................................................................... 7 3 Lateral area of face, or at least upper part, bare............................................................. 4 - Lateral area of face, or at least upper part, with long hairs, sometimes dense...................................... 6 4 Scape wider and longer than first flagellomere.............................................................. 5 - Scape equal to or narrower and shorter than first flagellomere............................... Cliorismia bussi (James) 5 Females with setae covering entire frons; males only distinguishable through genitalic comparison................................................................................................. Dialineura gorodkovi Zaitzev - Females with setae covering only dorsal two-thirds of frons; males only distinguishable through genitalic comparison...................................................................................... Pallicephala (3 species) 6 Male abdomen entirely whitish haired. Female frons with dark or dull, pale pubescence, never with shining calli............................................................................................ Acrosathe (2 species) - Male abdomen with at least a few black hairs. Female frons usually with shiny patch or large, shiny calli................................................................................................... Thereva (19 species) 7 Scape distinctly longer and wider than first flagellomere. Head strongly projecting anteriorly..... Tabuda planiceps (Loew) - Scape not longer and wider than first flagellomere. Head not strongly projecting anteriorly.......................... 8 8 Face with black band of pubescence extending from antennal sockets to eye margin......... Dichoglena nigrina (Krober) - Face without black band of pubescence extending from antennal sockets to eye margin............................. 9 9 Parafacial hairs present............................................................... Spiriverpa (2 species) - Parafacial area bare.......................................................... Pandivirilia conspicua (Walker) 10 Prosternum with hairs in and around central depression............................................................................................... Ozodiceromyia (2 species, plus 6 undescribed species known in collections) - Central depression of prosternum bare............................................... Psilocephala vicina Walker