140 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



Human parasitism is rare and of little consequence. Patton attrib- 

 utes the cases of intestinal myiasis known in India to the curious 

 purification rite of eating the five products of the cow, including a 

 small quantity of fresh dung, mixed together. Onorato (96) records 

 a case of enteric myiasis from Tripolitania ; as explanation of the 

 infestation, he says that the indigent poor often search through horse 

 dung for the undigested grains of barley which it contains, and that 

 the patient, who admitted having done that, may have contaminated 

 his own food with eggs or young larvae from his soiled hands. 



MUSCA DOMESTICA Linnaeus 



MUSCA VICINA Macquart 



Tlie Housefly ; the Typhoid Fly 

 (Fig. 82) 



The two species, or two varieties of one species, as they are vari- 

 ously considered by different authors, are treated together because 

 for our purposes it is impracticable to separate them. Their records 

 in the literature have been considerably mixed. The females are very 

 difficult to separate, if they can be separated with certainty at all; 

 the males of M. vicina have a much narrower front and a paler abdo- 

 men, although both these characters are subject to quantitative 

 variation. 



Recognition Characters. — Adults : The adult is easily distinguished from 

 other known species of Musca by tlie fact that the propleura are hairy (though 



sometimes with only a few hairs, and 

 rarely bare), the thorax has four 

 black vittae, and the abdomen, in 

 addition to the median stripe, is in- 

 fuscated on at least the third and 

 fourth segments. The eyes are bare, 

 the wing veins bare above and be- 

 low, the front at least broader than 

 the third antennal segment and with 

 distinct frontalia, the proboscis of 

 ordinary form, and the postsutural 

 dorsocentrals all strong. Length 

 6-9 mm. Larva (fig. 83) : Each an- 

 terior spiracle has five to seven 

 fingerlike processes; each posterior 

 spiracle has a well-developed peri- 

 treme of moderate width. 



Geographical Distribution. — 

 Practically world-wide. M. vicina is 

 apparently the form that occurs 

 throughout the warmer parts of the 

 Old World, including Africa, India, 

 and the warmer parts of the Palae- 

 arctic Region ; it also extends into 

 the New World, at least in the West 

 Indies. Since there is still consid- 

 erable question as to whether it is distinct from M. domestica, the following 

 records are for M. vicina and M. domestica combined: Nearctic Region. — 

 Alaska, Labrador, Quebec, Ontario, Manitoba, Saskatchewan, Alberta, British 

 Columbia, Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, 

 Connecticut, New York, New Jersey, Pennsylvania, Maryland, District of Colum- 

 bia, Virginia, North Carolina, South Carolina, Georgia, Florida, Mississippi, 

 Ohio, Michigan, Indiana, Illinois, Kentucky, Minnesota, Wisconsin, Iowa, 

 Missouri, North Dakota, South Dakota/Kansas, Louisiana, Oklahoma, Texas, 

 Montana, Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona, Oregon, 



Figure 82. — Musca domestica, adult male. 



