THE CANADIAN ENTOMOLOGIST. 197 



SYNOPSIS OF THE DIPTEROUS GENUS THEREVA. 



V,Y D. W. COQUILLETT, LOS ANGELES, CAL. 



The following table contains all the species of Thereva known to me 

 as occurring in this country north of Mexico. Thereva tergissa, Say. 

 (corusca, Weid.), and T crassicornis, Will (non Bellardi), belong to 

 Psilocephala. Thereva nigra, Say., is a true Thereva. T. albiceps, 

 Loew., is evidently the same as albifrons, Say ; and gilvipes, Loew., is 

 the other sex of flavicincta, Loew., as that author suspected at the time 

 of describing these two forms. Walker's and Macquart's species have 

 not been identified, nor could this be done with any degree of certainty 

 except by an examination of the type specimens. 



The table is as follows : — 



i. — Antennae black  3 



Antennae yellow ; California species 2 



2. — Pile and bristles of head and thorax wholly whitish, knob of 

 halteres yellow, front of female wholly opaque, .semitaria, n. sp. 



Pile and bristles of head and thorax largely black, knob of 

 halteres black, front of female with a shining black spot 



, fucata, Loew. 



3. — Femora largely or wholly black 5 



Femora yellow, knob of halteres black, front of female with one or 



two shining black spots 4 



4. — Front of female with two shining black spots, front of male desti- 

 tute of black pile duplicis, n. sp. 



Front of female with only one shining black spot, front of male 

 with many black pile flavicincta, Loew. 



5. — Knob of halteres black 8 



Knob of halteres yellow or white, front of female destitute of 



shining black spots 6 



6. — Front of female with two large, velvet-black spots, apices of 



femora black 7 



Front of female destitute of such spots, apices of femora broadly 

 yellow, cross-veins of wings not bordered with brown. 



, candidata, Loew. 



7. — Stigma dark brown, cross-veins bordered with brown, .otiosa, n. sp. 

 Stigma pale yellow, cross-veins not bordered via/is, O. S. 



