Reports to various 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, Eeading, the following Eeport was 
drawn up : — 
The so-called Cheese Skippers or Jumpers are the larvse of a 
small fly known as Piojihila casei, 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 larvae skip with 
considerable agility ; this is done by bringing the two ends of the 
body 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, 4 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 flies 
hibernate 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 larva 
to fly.” 
