man's chief competitors, the insects 6i 



insects. All the ichneumon wasps are parasitic, chiefly in 

 caterpillars, but some in wood-boring grubs, in saw-flies, bees 

 and spiders, in other parasites, in cockroach eggs, etc. It is 

 said ichneumons never hum so that they are able to sneak up 

 upon their prey unnoticed. Some curious wasps, with the 

 females mostly wingless and looking like large ants, live as 

 larvae in the nests of bumble-bees, parasol ants, etc., devouring 

 their young, or in various large beetles, or in other insects. 



Of all the insect parasites the flies are the most nearly uni- 

 versal in their tastes. The great majority of tachinid flies 

 when young live in the caterpillars of moths and butterflies. 

 I raised some scores of these this summer, quite without in- 

 tention on my part. Others live in bees and wasps, in grass- 

 hoppers and bugs, and even in other flies and earth-worms. 

 The bee-fhes proper, or bombyliid flies, are mostly parasites 

 on solitary bees and bumble-bees, or in the latter case pos- 

 sibly nest scavengers. But some Uve in other hosts, and 

 and among our native kinds a few of the commonest live in 

 the young of tiger beetles. 



Toads, frogs, turtles, young birds, and many mammals, 

 especially the grass feeders, are subject to the attacks of 

 numerous flies the larvae of which live in open sores or just 

 beneath the skin. Other fly maggots live in the nostrils and 

 air passages in the head, or in the alimentary tract. Repre- 

 sentatives of all these sorts are also found in man and often 

 cause great pain and even death. Other fly maggots live in 

 greasy wool; and a whole group of strange flies which are 

 curious in laying fully developed young or even pupae instead 

 of eggs are blood suckers on birds and bats and some other 

 mammals, hke large and active lice. Some of these have 

 wings, some have abortive wings, and some are wingless or 

 shed their wings. The most curious one of all, caUed Ascodip- 

 teron, which lives on bats, after shedding its wings bores under 

 the skin of its host and transforms into a soft spherical lump 

 with not the slightest resemblance to any insect. A minute 

 wingless fly occurs on bees. 



