344 
The Two-winged Flies 
larval skin, and issue as adults in ten or twelve days after birth. The blow¬ 
flies and bluebottles, members of this subfamily, have the body steely blue or 
greenish and are great buzzers. The blow-fly, Calliphora erythrocephala , 
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 sarracenicc. (After Lugger; natural size 
indicated by line.) 
larvae feed on the juices of the decaying meat and pupate after a few days. 
The pupae enclosed in the thickened brown last larval skin look like 
large smooth shiny brown elliptical seeds, as do indeed the pupae of all 
Calyptrate Muscidae. The commonest bluebottle- or greenbottle-fly is Lucilia 
cczsar, 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, 
Compsomyia macellaria, which 
lays its eggs on flesh, manure, in 
open 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 larvae fairly eat away the whole inner nose and upper 
Fig. 490.—Diagram of wing of Lucilia ccesar, 
showing venation. 
