THE BLOW FLIES 
253 
ous species and liable to carry intestinal diseases. Their 
larvae as a rule feed in excreta or in decaying flesh, but 
a bluebottle fly in a milk jug is no more dangerous 
than a house fly in the same situation. 
Lucilia ccesar L. (Fig. 28) is a common and wide¬ 
spread form, abundant in both Europe and North 
America, and is one of several species of the shining 
green or bluish flies commonly found about dead ani¬ 
mals and different kinds of excreta. It is not ordinarily 
found in houses, but may be driven in at the approach 
of a heavy storm, just as is the case with the biting 
house fly. On May 17, 1899, for example, a heavy 
storm occurred about four p.m., and the next morning 
twenty-eight specimens of this species were found to 
have come into one of the rooms of my office. In 
Europe L. ccesar is known as the “greenbottle fly,” and 
is almost exclusively a carrion feeder. 
Calliphora erythrocephala Meig. (Fig. 29) is an¬ 
other widespread species common to Europe and North 
America. It is a large bluebottle fly of rather dull 
color with black spines on the thorax. It is the com¬ 
mon blow fly of Europe and is the species treated by 
Lowne in his classic work on the anatomy of the blow 
fly. Its lame are indistinguishable from those of the 
greenbottle fly. The eggs are laid on meat and dead 
animals and even upon dead insects. The species is 
unusual from the enormous number of eggs laid by a 
single female. The Russian author, Porchinsky, re¬ 
cords from 450 to 600 eggs from a single female. 
Hewitt records the duration of a single generation as 
