The Two-winged Flies 333 



the cheese-skippers and pomace-flies (Muscidae acalyptratae) are about the 

 only names in the list of these hundreds which seem at all familiar. The 

 flower-flies (Syrphidae) and bee-flies (Bombyliidae) are numerous, often 

 seen, and, what is more, often definitely noted and admired, but "beautiful 

 flies" is about as specific a name as they ever get. The bristly parasitic 

 Tachinid flies are noticed now and then by the nature student, and the 

 dancing Empidids interest, in a decided but irritating way, drivers and 

 bicyclers in the dance-fly mating-time. But even entomologists, professional 

 as well as amateur, unless they are special collectors and students of 

 Diptera, recognize but few of the hosts of small flies that fill the air during 

 the long summer days. 



In the above key only the larger and more commonly represented families 

 are included, so that it will be possible for a collector using this book to 

 find himself possessed of a fly which will prove intractable when an attempt 

 is made to classify it into its proper family. But such unfortunate happen- 

 ings will be very infrequent, as only small families of obscure or rare species 

 are thus omitted. 



Poised almost motionless in the air a few inches above a sunny path or 

 roadway, or darting away, when disturbed, with lightning swiftness and 

 having all the seeming of bees, hairy, plump-bodied, and amber-colored, certain 

 bee-flies (Bombyliidae) are rather familiar acquaintances of the summer field 

 student. Other bee-flies, as swift 

 and as beautiful, are less bee-like 

 because of the striking "pictures" 

 in the wings, blackish or brown 

 blotches conspicuous in the thin, 

 otherwise clear wing-membrane. 



Some of these bee-flies have an r 



... , . riG. 466. Diagram of wing of Anthrax ful- 



unusually long slender proboscis v iana, showing venation. 



held straight out in front of the 



head like a spear at rest (Fig. 467). But this beak has no blood thirstiness; it 

 is used to suck up sweet nectar from flower-cups. The larvae of the bee-flies, 

 however, are carnivorous, living parasitically in the egg-cases of grasshoppers 

 or on the bodies of wild bees and various caterpillars. One of these bee- 

 fly larvae burrowing into a grasshopper's egg-pod can do awful harm to the 

 embryo grasshoppers, but at the same time much good to us, by the satisfac- 

 tion of its egg-eating propensities. Beautiful, velvet-clothed, swift-winged, 

 and nectar-feeding as a fly, maggot-like and parasitic as larva, the bee-fly 

 is a good example of the great differences in structure and habit which are 

 possible between young and old of the specialized insects. 



Bombylius (Fig. 467) is a genus in which the proboscis is very long and 

 slender, the body short and plump and covered with a thick soft coat of longisb 



