Reports to variotts Correspondents 107 



The Cheese Fly. 



(^Piophila casei, L.) 



In answer to a request for information (concerning the Cheese Fly 

 {Piophila casei) from Mr. C. W. Walker-Tisdale, of the Dairy 

 Department, University College, Keading, the following Report was 

 drawn up : — 



The so-called Cheese Skippers or Jumpers are the larvffi of a 

 small tly known as Piopliila rasd, Linn. Like most household 

 animals, it is cosmopolitan. 



The Cheese Fly is a small black glistening fly, about three- 

 sixteenths of an inch in length, with transparent wings. 



It lays its eggs in compact masses of 100 or more, and also 

 singly. Often as many as twenty may, however, be found together. 

 Exactly how many each female may deposit is not known ; Miss M. 

 E. Musfeld, the American authority, says thirty was the average 

 number deposited by the females in her breeding-jars. The egg is 

 white, slender, and oblong, and about one-twenty-fifth of an inch 

 long. It may be deposited not only in cracks and crevices of cheese 

 and in the curd, but also upon hams and bacon. The period of 

 incubation seems to vary between thirty-six hours and four days, 

 according to the climate and time of year. 



The maggot or larva is creamy- white, cylindrical, narrowed to a 

 point towards the front end and bluntly truncated posteriorly, with 

 two fleshy filaments and two horny stigmata. The larvte skip with 

 considerable agility ; this is done by bringing the two ends of the 

 Iwdy together and then suddenly releasing them. 



The maggot lives from seven to fourteen days, according to the 

 time of year. When full-grown, the maggots reach from 7 to 9 mm. 

 They then find some dry crack in the cheese, and become converted 

 into a golden brown puparium, •! to 5 mm. long. In about ten days 

 the fly emerges, and starts a fresh generation. There are as many as 

 three generations during the year. As a rule, the winter is passed 

 by the maggot in the puparium stage, the larva changing into the 

 pupa in the spring. It also seems that a certain number of flics 

 liibernate in pantries, sheds, etc. 



All windows where cheeses are kept should be closely screened, 

 and made to prevent the flies from entering. 



Mr. Walker-Tisdale pointed out " that the time it took the eggs 

 to hatch out was very variable, and also the other stages of Inrva 

 to fly." 



