ORDER VII. TWO-^VINGED 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 antenna?, 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 ofl*, 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, tlie 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, etc., 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 

 antennas 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 



