156 THE BLOW-FLY. 
species of blow-, meat- or flesh-flies belong here. But some of 
them are not satisfied with simply trying to obtain food for 
themselves, but take care of their offspring by dropping 
either eggs or larvee upon the host. Many species of blow- 
flies have this habit, and as they produce living young and 
as these increase rapidly in size, they can cause trouble, even 
death. The viviparous females retain the eggs in spiral 
dilations of their oviducts until hatched, when they are de- 
posited upon decaying flesh of all kinds. The sexual organs 
of the horse, cattle, and hogs, the interior of the ears, but 
principally wounds and sores are selected by such flies and 
here they drop living maggots in large numbers. Whoever 
has observed even fairly fresh meat exposed for but a few 
moments in places where blow-flies abound must have seen 
the innumerable small heaps of very minute maggots de- 
posited upon it. The female flesh-fly (Sarcophaga carnaria 
Linn.) can deposit at least 20,000 of these maggots, and as 
they grow very rapidly they consume a large amount of food, 
and foreing their way into the festering substance about 
them they soon enlarge sores (‘“‘living sores’’), and make them 
very dangerous. All these flies multiply very rapidly, pro- 
ducing many generations during the course of a warm season. 
It has beencomputed that a single female, within six months, 
can have 508,000,000 descendants. No wonder, then, that 
they can devour the carcass of a large animal in a few days, 
and that we have so many flies about dwelling-places 
and stables not kept clean. 
The maggots of these flies grow so rapidly, if food is 
plenty, that froma mere speck they grow in two or three 
days to half an inch in length. They are whitish, long, soft-. 
bodied, footless, and are smaller towards the head and 
thicker and blunt behind. When full-grown they leave their 
odoriferous food and crawl to some convenient spot, force 
their way into the soil, where they contract into elongated- 
oval, barrel-shaped, and reddish-brown puparia, inside of 
which the adult insects are formed. This requires but a very 
short time, a few days, and the winged fly issues ready to 
start another generation. Fig. 130, plate X, illustrates this 
common insect. 
