444 Observations on Habits and Parasites of Common Flies 
the cage together with food and water between September 1 and 
October 7, 1914. About 70 flies emerged during October, but no 
living flies were present in the cage after November 18. 
Between April 29 and May 22, 1915, 308 blow-flies, 140 males and 
168 females, emerged. As in an experiment previously described the 
males appeared at first in greater numbers than the females, 53 males 
and 38 females emerging between April 29 and May 6. After that 
date 87 males and 130 females appeared. In another open air cage 
of the same type 206 blow-flies emerged between April 24 and May 16, 
and subsequent generations were bred from them (p. 458). 
In other experiments carried out in the same way in large open 
air cages 41 specimens of Fannia manicata*, 26 males and 15 females, 
emerged between April 24 and May 10, specimens of F. canicularis* 
about May 4, and 14 specimens of Ophyra leucostoma, 9 males and 
5 females, between June 4 and 13. Eight of the nine males emerged 
before the first female. A pupa from the earth in this cage, brought 
into the house, emerged 13 days before any of those left on the 
ground. 
It is of some interest to note that the sexes emerged in nearly equal 
numbers in all the experiments, for example, 656 (48-9 %) male and 
684 (51-1 %) female blow-flies emerged. Another interesting point is 
the relatively early emergence of the males, especially in the genera 
Calliphora, Fannia and Ophyra. 
During the late summer and autumn of 1914 a large number of 
house-flies were kept in a large gauze cage, 6 x 6 x 10 ft., erected 
outside on bare earth. The flies lived and bred 1 in this cage from 
June 21 till Oct. 9 when the last survivor died. It was hoped that 
some of the pupae might give rise to flies in the following year and so 
decide the mode of wintering of the house-fly. Unfortunately the 
food for the larvae was placed in depressions in the ground, and the 
heavy rain which fell on Oct. 15 flooded these hollows possibly causing 
a considerable mortality amongst the larvae. Nevertheless some 
living and healthy looking larvae were seen subsequently. Many of 
these, however, seem to have been destroyed by the heavy rain of 
Oct. 31, for on Nov. 4 many dead and sodden larvae and pupae were 
noticed amongst the remains of the food. Unfortunately also a female 
II. dentipes gained entrance and deposited her eggs. The Hydrotaea 
larvae being carnivorous doubtless destroyed many of the Musca 
1 As specimens caught in the house were being added frequently, it is doubtful whether 
any eggs were laid by flies which emerged and spent their whole lives in the cage. 
