FLIES 



and then change into chrysalides. After five days a 

 full-grown fly emerges from the chrysalis. A female 

 fly lays a batch of about 120 eggs, and often a second 

 lot before she dies. Flies, which are born in the 

 spring, will often survive until the cold of late autumn 

 kills them. Apart from being an intolerable nuisance 

 in houses and to stock animals, the house fly is an 

 agent in the spread of disease germs amongst men and 

 domestic animals. It carries the germs of diseases on 

 and in its body. It is one of the foulest of feeders. 

 Unfortunately for men, its digestive juices are not 

 sufficiently antiseptic to kill disease bacteria swallowed 

 with its food. They, consequently, pass out of it in 

 its excrement alive. Fly specks are the excrement of 

 flies, and they usually teem with living disease germs. 

 Wild birds feed eagerly on the fly in every phase of 

 its life history. Many species of birds devour the 

 maggots and chrysalides, while others take the adult 

 fly on the wing. 



The maggots of the flies known as gall midges 

 (Cecidomyid<e) burrow into the tissues of plants and 

 give rise to galls. 



The crane flies or daddy long-legs (Tipulid*) 

 are notorious pests. Their larvae or maggots, which 

 are known as leather jackets, prey upon the roots of 

 plants. 



The female gadfly (Talamid^) sucks the blood of 

 horses and cattle, and in so doing carries disease from 

 one to another. The maggots live in damp earth, 

 and are preyed upon by partridges, thrushes, robin 

 chats, and other birds. The hairy, bee-like botflies 



259 



