344 



The Two-winged Flies 



larval skin, and issue as adults in ten or twelve days after birih. The blow- 

 flies and bluebottles, memi)ers of this subfamily, have the body steely blue or 

 greenish and are great buzzers. The blow-tly, CaUiphora erylhrocepliulti, 

 has the thorax black and abdomen steely blue. Its eggs are laid on exposed 

 meat, fresh or decaying, such egg-infested meat being called "blown." The 



Fig. 489. — A blow-fly or flesh-fly, Sarcophaga sarracenia. (.After Lugger; natural size 



indicated by line.) 



larvas feed on the juices of the decaying meat and pupate after a few days. 

 The pupa; enclosed in the thickened brown last larval skin look like 

 large smooth shiny brown elliptical seeds, as do indeed the pup« of all 

 Calyptrate Muscids. The commonest bluebottle- or greenbottle-fly is Liidlia 



cccsar, which lays its eggs in 

 cow-dung as well as on flesh, 

 and which often comes into 

 houses, particularly before rain. 

 A flesh-fly of .serious importance 

 is the terrible screw-worm fly, 

 Compsomyid maccUaria, which 

 lays its eggs on flesh, manure, in 

 oi)en wounds, and often in the 

 nasal passages of domestic animals and human beings, entering the nose for 

 this purpose while the unfortunate person or animal is asleep. Numerous 

 frightful cases of such attacks on persons are recorded, especially from the 

 southern states. The larvK fairly eat away the whole inner nose and upper 



Fig. 400. — Diagram of wing of Lucilia ctrsar, 

 showing venation. 



