FIELD BOOK OF INSECTS. 



17. Third longitudinal vein deeply curved into the first 

 posterior cell. Several genera; of which Helopliilus has 

 thickened hind femora, the face is not protuberant, and the 

 third antennal joint is oval. It has been reared from 

 brackish water as well as from carcasses. 



Third longitudinal vein only gently curved 18. 



1 8. Thorax with distinct yellow markings other than 

 on the shoulder protuberances. Wasp-like flies of large 

 size 19. 



Not so. Numerous genera, some not rare. 



19. Hind femora with a conical, tooth-like protuberance 

 below, near the outer end; sixth longitudinal vein directed 

 obliquely outward beyond the anal cell. Spilomyia. 



Not so. Antennas inserted low down, near middle 

 of head's profile; face not longer than the front: Tem- 

 nostoma (Plate LXVIII). Antennas inserted on a conical 

 process; face much produced downward: Sphecomyia. 



20. Third longitudinal vein deeply bent into the first 

 posterior cell. Hind femora with a sharp, tooth-like 

 projection below, near outer end: Miiesia (Plate LXVI). 

 Hind femora without such tooth, although sometimes 

 thickened: Eristalis (see below). 



Third longitudinal vein not deeply bent; third 

 antennal joint elongate; arista feathery. Volucella (see 

 below). 



V. evecta (Plate LXVI) differs from its 

 Volucella congeners by being furry. F. obesa is 



brilliant shining green; the wings are spotted at the end of 

 the auxiliary vein and on the cross- veins; lives in and 

 near the Tropics. V. fasciata is black with yellow markings 

 on the thorax and three rather broad yellow bands on the 

 abdomen; the wings have indistinct dark bands. Some 

 say that the larvae of Volucella feed on the larvae of bumble- 

 bees and wasps but probably they are merely scavengers 

 in the nests of these Hymenoptera. 



About the middle of the i8th Century 



Reaumur, known also for his thermometer, 

 tenax 



wrote voluminously, and exceedingly well, 

 on life histories of insects. It was he who called the larva 



256 



