TWO-WINGED FLIES AND FLEAS 101 



juices from flowers. The life-history of this insect 

 was long unknown, and the details still call for in- 

 vestigation. It has been ascertained, however, that 

 the eggs are jerked by the parent fly, when hovering, 

 against a bank in the vicinity of a solitary bee's nest, 

 and that the Bombilius larvae feed as parasites on the 

 bee-grubs. 



The second sub-order 1 of the Diptera comprises an 

 enormous number of highly specialized flies, whose 

 metamorphosis is very great, the larva being usually a 

 maggot with no definite head-capsule. In the extreme 

 type the maggot has a broad, bluntish tail-end, and 

 tapers almost to a point at its anterior extremity, 

 where the mouth-orifice is situated. Here, also, we 

 find a pair of strong hooks, moved by powerful muscles, 

 that serve to tear up the food substance, on the juices 

 of which the larva subsists. When one of these 

 maggots is full-fed, its skin, instead of being cast aside, 

 contracts and hardens to form an ovate puparium a 

 kind of protective case within which the pupa lies. Ulti- 

 mately the perfect fly pushes open a circular lid at 

 the head-end of the puparium, and creeps out. 

 Throughout this sub-order the species have incon- 

 spicuous, three-jointed antennae, of which the third 

 joint is by far the largest, and bears a long, bristle-like 

 process. In many genera there is a conspicuous lobe, 

 called the squama, at the base of each wing. The most 

 important families are the following : 



The hover-flies and their allies 2 differ from all other 

 Diptera in their wing-neuration, but in other respects 

 the numerous species vary greatly among themselves. 

 Some are hairy, others smooth and shining, while many 

 are banded or spotted with yellow or orange, and are 

 1 Cyclorrhapha. 2 Syrphid&. 



