THE CHEESE SKIPPER AS A PEST IX CURED MEATS 49 



on the meat after the last record of a temperature of 100° F. ; that is, 

 during the second period. But the ends of these records did not 

 always coincide with the removal of the meat from the smokehouse ; 

 the thermograph was frequently taken from the smokehouse hours 

 before the meat was removed. 



Wilder and Davis (79, p. 366) directed that the fire should be put 

 out when the smoking is completed, the house opened up, and the 

 meats allowed to cool. These writers realized, however, the danger 

 of exposing meats in unprotected smokehouses, and recommended 

 (p. 371) that the windows and doors be finely screened, and that 

 smokehouses should be regularly fumigated with sulphur. 



While smoked meats are cooling off in the smokehouse, they are 

 not only at maximum attractiveness for skipper flies but also readily 

 accessible to the flies when unscreened doors, windows, or ventilators 

 are left open. The writer has observed skipper flies upon meats in 

 the smokehouse at this stage, and recommends that the houses be of 

 tight construction and thoroughly screened with wire cloth of at 

 least 30 meshes per inch. 



SUMMARY AND CONCLUSIONS 



Piophila casei (L.), a piophilid fly commonly known in its larval 

 or maggot stage as the cheese skipper and ham skipper, and by other 

 popular names, is widely distributed throughout the world. In the 

 United States it is the chief insect pest in smoked, cured pork, and 

 cheese. It is able to nourish itself in dried beef, salt pork, cured fish, 

 and a variety of inedible animal products. 



Medical literature contains records of myiasis caused by the pres- 

 ence of skipper larvae in the intestines, a condition which probably 

 not infrequently results from the custom of eating infested cheese. 

 There are several published accounts of the presence of this species 

 in exposed human corpses and its remains have been found in graves. 



The characteristic injury done to cured hams and shoulders con- 

 sists of eaten-out areas among the large muscles, and these extend to 

 the center of the meat, close to the bones. Very fat meat, such as 

 bacon, is not extensively injured; the insect prefers connective and 

 muscular tissue. 



The adult is a very active, small, tame, shining black fly some- 

 what resembling a winged ant. It feeds principally on the juices of 

 the larval food, and liquid or semiliquid food is a prerequisite to 

 normal oviposition. 



Fertile eggs are laid as soon as lO 1 /^ hours after the act of mating, 

 the latter often taking place a few minutes after the female leaves 

 the puparium. Unmated females deposit infertile eggs. The eggs 

 are rapidly scattered about over the surface of the meat or masses 

 of them are concealed in crevices. The maximum number of eggs 

 ]aid by one female is nearly 500, but the usual number is about 140, 

 laid over a period of three or four days. 



Flies kept at low temperatures (48 to 50° F.) may live for more 

 than a month. During hot weather (80 to 90° F.) the usual length 

 of life is three or four days if food and water are not provided. 

 When flies are unfed the females live longer than the males: the 



