INSECTA : DIPTERA 



331 



FIG. 249. The Blow-fly 

 (Calliphora vomitoria). ( x 2. ) 



The Blow-fly The Blow-fly (Calliphora vomitoria), with its 

 or Blue- shining blue abdomen, is common everywhere, 

 bottle. rp]^ j on g narrow eggs are laid on meat, perhaps 

 200 of them together, 

 and the legless mag- 

 gots, known to anglers 

 as "gentles," bury them- 

 selves in the meat, and 

 eat voraciously for four 

 or five days, by which 

 time they are full grown. 

 Each maggot then bur- 

 rows in the earth if 

 possible, or retires to 

 the most sheltered 

 corner available, contracts its body to a regular, oval shape, 

 and then, without casting its larval skin, enters the resting 

 stage. The skin hardens and turns brown, and the body 

 within undergoes the same curious dissolution as in the 

 House-fly. In four or five days, however, the white pupa is 



to be found within, 



A __ kn^rh of larva B^^_, . an d in time this 



breaks one end of 

 the enclosing co- 

 coon by beating on 

 it with its head ; 

 then, pushing off 

 the end as a little 

 cap, the fly em erges ; 

 soon its wings ex- 

 pand, its colour darkens, and it flies off to find a mate. 



The Tsetse -fly (Glossina morsitans), which is 

 fl se ' e " such a serious plague in Central and East Africa, 

 is closely allied to the Blow-fly. It pierces the 

 skin and sucks the blood of cattle, and in so doing intro- 

 duces into the blood of the healthy animal, the germs 

 of a disease known as " nagana " or " fly-disease." Where 

 these flies abound, this disease may exterminate whole herds 

 of cattle. 



FIG. 250. Stages in the Life of the Blue-bottle. 



A, Eggs ; 11, larva or maggot ; C, pupa. 



