288 THE BRITISH NATURE BOOK 



Sub-order ii. CYCLORRHAPHA. 



To this belong the Hover-flies (SyrphidcB), which resemble to a remarkable 

 degree both wasps and bees. They may be frequently seen in our gardens, 

 where the perfect insects feed upon pollen chiefly, and the larvse (in many 

 species) prey upon aphides. The name is derived from the familiar and 

 characteristic hovering of the insect, poised over flowers. The eggs are 

 deposited on leaves, and the larva, armed with a three-pronged beak, sucks 

 the juices from aphides, until *it changes into the pupal state, in which, 

 attached to some leaf, its skin becomes horny and golden-brown in colour. 



BOT-FLIES ((Estridce) 



are hairy, bee-like insects, the larvae of which actually live in the bodies of 

 large animals. The Horse-bot lays her eggs on the hair of horses, where they 

 (or the larvse) remain till licked off. Then they live in the stomach all the 

 winter, the mouth of the larva being furnished with two hooks, by means 

 of which it clings to the inner coat of the horse's stomach. In the next 

 summer it loses hold, and passing out of the horse burrows in the ground, 

 where it assumes the pupal form. The Ox-bot or WARBLE-FLY is the most 

 troublesome of all, much resembling a small humble bee, with whitish face 

 and abdomen, the latter crossed by a band of black. The female pierces a 

 hole by means of its remarkable horny " telescopic " ovipositor in the hide 

 of an ox's back, in which an egg is placed. Cattle rush wildly about to escape 

 her attentions ; for the larva under the skin does great injury, causing a 

 warble or sac of matter to form. 



The Sheep-bot is the most serious of all these pests, laying its eggs in the 

 nostrils of the sheep, the larvae sometimes getting into the brain. 



Muscidce form an enormous family, which includes the Common House-fly 

 (Musca domestica}. 



The briefest reference must be made to the Tachnid Flies, bristly-headed 

 insects, whose larvae, like those of the Ichneumon, live upon living caterpillars ; 

 and the Grey Flesh-flies, which actually produce their larvae alive (not in 

 eggs), and place them on animal refuse. 



The House-fly is a pest so well known as to require no detailed description, 

 but by all means examine it under the microscope, and note the marvel and 

 beauty of its parts. Beyond any question this insect is, as Mr. F. W. Fitz- 

 simmons, F.Z.S., calls it, a " slayer of men," in that it disseminates disease. 

 From one single house-fly 100,000 faecal bacteria have been discovered, and 

 it must be obvious that a foul creature that settles on our food, bread, milk, 

 meat, etc., is most dangerous to health. Every larder ought to be fly-proof 

 on this account, and all refuse and garbage near a house or a town should 

 be methodically destroyed. Each female can lay 1,000 eggs, and thus, by 



