442 Observations on Habits and Parasites of Common Flies 
While it cannot be claimed that these problems have been settled, 
the greatest care has been taken to render the data recorded as accurate 
as possible, and undoubted advances have been made towards a better 
understanding of the circumstances which influence the lives of flies. 
Experiments of the kind about to be described require continuous 
attention throughout the season, and are very laborious, but seem 
to furnish the only means by which knowledge of sufficient accuracy 
to be of real value for practical purposes can be gained. 
The wintering habits oe flies. 
There has been much controversy as to the manner in which house¬ 
flies ( M. domestica) survive the winter, some assuming that the species 
is perpetuated by the few which hibernate, and others that the winter 
is passed in the pupal stage. No very satisfactory evidence seems to 
have been brought forward in support of either view, though some 
attempts have been made to decide the question by experiment. 
Whatever doubt there may be about the house-fly passing the winter 
in the pupal stage, there can be none in regard to many of the common 
species which frequent the neighbourhood of houses. 
In the autumn of 1912 the writer collected three samples of dog 
faeces and placed them in separate jars half filled with earth. The 
tops of the jars were closed with gauze, and the jars were put outside 
in a sheltered place during the winter. On March 25, 1913, the jars 
were examined. The first contained 110 pupae, the second 215, and 
the third 245, or 570 in all, of which 133 were large, 427 small and 10 
of the Fannia type. These pupae were kept in a warm room, and from 
the large specimens flesh flies ( Sarcophaga melanura*) emerged between 
April 4 and May 9, and from the smaller Anthomyia radicum* during 
the first three weeks of April. 
On March 28, 1914, damp soil near a manure heap was examined, 
and at a depth of about three inches several large and small pupae 
were found. From these pupae, which were kept in a warm room, 
C. erythrocephala and one 0. leucostoma emerged between April 4-22. 
In the soil close to a second heap, which was situated in an open field, 
a number of smaller pupae were found. From these Anthomyid flies 
emerged. 
During the winter of 1914-15 many experiments were carried out. 
In October, 1914, flies were allowed to deposit their eggs on the carcases 
of small animals placed on dry earth and kept in two galvanised iron 
