ORDER VII.—TWO-WINGED INSECTS, OR FLIES. 309 
nurseries. This, however, is a great mistake; for although 
they abound in filthy localities, it is only because the fe- 
male has selected as a place of deposit for her eggs those 
places where they will be safe and furnished with a plenti- 
ful supply of food as soon as hatched; hence the damp 
cracks in floors are often chosen. The process of their de- 
velopment may be observed with ease and accuracy by put- 
ting some fleas with the black dust of decayed trees into a 
glass bottle, the opening of which is then covered with a 
magnifying glass. The female will soon be seen to deposit 
about twenty white, oval eggs, from which, after six days 
in summer, and twelve days in winter, small; white, snake- 
like maggots will proceed, which are scarcely one line long, 
but whose bodies are composed of thirteen hairy ringlets, 
and their heads provided with two short antennz, a mouth, 
and two eyes. At the extremity of their hind bodies are 
seen two yellowish, fine bristles, which assist them in their 
serpentine motions. Most of the time they creep about, but 
if disturbed immediately conceal themselves. They must 
be fed with flies, of which the head is taken off, or with 
dried, pulverized blood. Under the solar microscope they 
appear ten feet long, and of course all their motions can be 
distinctly seen. In about two weeks they acquire their full 
growth, when they conceal themselves in the ground and 
metamorphose into a pupa, from which, about a week aft- 
erward, the perfect flea issues. The female flea drops her 
eggs any where she happens to be, but in preference upon 
heaps of manure, in the cracks of dirty floors, etce., on which 
account it is well to wash the floors with boiling water 
wherever they have appeared. , 
The head of the perfect flea is disproportionably small, 
and the eyes still much smaller, round, and shining. The 
antennz are club-like in form, and the alimentary organ 
consists of a long, hollow sucking-sting, which probably 
represents the jaws. The whole body consists of twelve 
