502 Observations on Habits and Parasites of Common Flies 
to prefer surfaces almost in contact with the ground, natural openings, 
such as the mouth, nose and ears, or wounds. 
Occasionally they were seen feeding in great numbers on old 
artichokes, which had been turned up from the ground. 
For some considerable time before settling down for the night nearly 
every fly is occupied in “blowing bubbles,” repeatedly regurgitating 
a large drop of fluid, and sucking it back again. This procedure is 
less commonly seen at other times of the day. 
(b) “ Wild” flies. 
Wild flies behave very similarly. They are seldom active before 
8.30 a.m. and are most active on sunny days. On cold autumn days 
with sunny intervals they were seen to emerge from crevices and sun 
themselves (PL XXIII, figs. 29, 30), and in oppressive weather they 
behaved in unusual ways. Specimens were seen “bloving bubbles” 
almost daily. 
It is evident, therefore, that much, otherwise difficult to ascertain, 
may be learnt about the habits of “wild” flies bv observing the be¬ 
haviour of captive flies in large cages out of doors. 
It is impossible, however, to study some of their habits in cages. 
On warm sunny days with little or no wind many species settle on 
certain flowers, but seldom resort to flowers on very hot, dull or windy 
days. When flies are emerging in large numbers very soft, young 
specimens are common on flowers. In the spring hawthorn flowers are 
a great attraction to many species. On the approach of an observer 
specimens of many species sitting on flowers, palings, walls and other 
situations crouch closer and approximate their wings more closely 
together, apparently with the intention of making themselves less 
visible and escaping detection. 
Flies belonging to the genus Lucilia and 0. leucostoma seem to be 
peculiarly active in sunshine, and are seldom seen in large numbers 
except on warm sunny days. The males of 0. leucostoma hover in the 
air like some of the Syrphidae. 
The larvae of common flies. 
A considerable number of observations were made on the habits of 
the larvae of some of the common species, but as it is proposed to carry 
on further investigations during the coming season only certain observa¬ 
tions of special interest will be recorded. 
In many species the tendency to migrate, especially in wet weather, 
is very marked, even when the food supply is abundant, and special 
