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 
unusually long slender proboscis 
held straight out in front of the 
head like a spear at rest (Fig. 467). But this beak has no bloodthirstiness; 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 
Fig. 466.—Diagram of wing of Anthrax fuU 
viana, showing venation. 
