FLIES. 429 



Several instances have been reported of larvae, probably of Dermatobice, being 

 found in the human flesh. It is probable that these, or larvae of Hypoderma, when 

 accidentally placed on the skin, bore in, but it is not probable that the fly deposits her 

 eggs on the human body except possibly when deceived by an odor conveyed from 

 cattle or horses. 



The very large family of Muscid^ comprises more than a third of all the known 

 flies. The antenna always consists of three joints, the third of which has a simple 

 or feathered bristle on its upper border ; there is no false vein in the wings. They 

 show a considerable variation and are divided into numerous sub-families, which by 

 some entomologists are considered of family rank. In America they have been but 

 little studied, the larger portion being yet without names. 



In the Muscince the first posterior cell is much narrowed or closed, and the bristle 

 of the antennas is feathered to the tip. The common house-fly {Musca domestica) will 

 readily serve as an example. In this species the larvae are simple maggots without 

 legs or head, and with two or three booklets at the mouth. They are more slender in 

 front, smooth, shining, soft, naked, and more or less transparent, and about eight 

 or nine millimeters in length. They are found in almost every kind of decaying 

 vegetable or animal mattei", such as offal, manure, dead animals, even spittoons that 

 are filled with tobacco ; indeed filth in any form is the home of these disgusting crea- 

 tures. They crawl readily about by the extension of the terminal part of the abdomen, 

 and easily find their way into the interior of moderately firm substances. The eggs 

 are laid in groups together, about eight days after pairing, and in from twelve to 

 twenty-four hours the young larvae make their appearance. Each female lays about 

 seventy eggs. In about fourteen days the larvae attain their full size, when they crawl 

 into some dry or protected place and contract into larvigerous pupae, in which stage 

 they remain for one or two weeks before appearing as perfect insects. This fly is 

 perhaps the most cosmopolitan in the whole order, being found in almost every part 

 of the world. Their food consists of whatever they can suck up through their fleshy 

 proboscis, or can scrape off with their roughened labellre and dissolve with the 

 saliva. 



Another fly as well known as the preceding species, and equally detested by the 

 housewife, is the blow-fly, Calliphora vomitoria. It is larger than the house-fly, black 

 in color, with a steel-blue abdomen that shows delicate white, 

 shimmering markings in different reflections. The flies are 

 attracted very readily by the odor of cooking meat and 

 vegetables, and are very noticeable in their loud buzzing and 

 aimless flight against the window-panes. Scarcely any pre- 

 cautions will pi'event them from depositing their eggs in 

 fresh or decaying flesh, cheese, or nitrogenous vegetables. 

 Great numbers of the eggs are laid, whether singly or in 

 clusters. They hatch in about twenty-four hours, and the 

 voracious myriads of maggots soon consume the substances FiG.nm. — CaiHpiwravnmUoria, 

 in which they live, and then as readily devour each other. enlarged. 



They attain their full development in a few days, and then, as in the house-fly, crawl 

 aside into some protected spot and transform into pupae. 



The screw-worm fly ( Compsomyia macettaria) belongs to this group, and is found 

 from Patagonia to Canada. It is a bright metallic green fly, with golden reflections 

 and four black stripes on the upper part of the thorax, measuring about one-third of 



