470 Observat ions on Habits and Parasites of Common Flies 
The house-fly, M. domestica, enters dwellings more persistently than 
any other species, and behaves in rooms in a totally different manner 
to any other fly. Many specimens caught in rooms are quite soft 
showing that they have entered shortly after emerging from pupae. They 
behave in houses as if thoroughly at home, penetrating to every part 
of the room and seldom visiting the windows. They move about 
examining everything, often in a leisurely manner, feed whenever 
opportunity offers, are often seen mating and rest for the night on the 
furniture. 
While other flies seem dazed in artificial light, house-flies behave 
in exactly the same manner as in daylight, and are not attracted to the 
source of the light. 
In fact every circumstance of their behaviour points to design in 
their entry and occupation of rooms. 
In 1915 house-flies first began to enter the dining room on June 6 
and continued to do so in small numbers almost daily up to the end of 
July. It is a remarkable fact that the 15 house-flies, mostly soft, 
newly emerged individuals, which entered during June were all males. 
In 1914 five out of the first six were males. This fact tends to 
support the view that the house-fly passes the winter in the pupal 
stage, since in alhed species males appear from winter pupae earlier 
than females (p. 444). 
During July 1915,25 house-flies, of which 17 were males and 8 females, 
were caught in this room, and in August 142, of which 82 were males 
and 60 females. In September the numbers increased considerably, but 
owing to the fact that the records from the 13th to the 18th are imperfect 
the total cannot be stated. Of those caught 90 were males and 59 
females. During October the numbers increased further, 174 males 
and 284 females being caught in the room, but in November only 
8 house-flies, 3 males and 5 females, entered the room (Chart 3). 
Up to the end of September 60 % of all the house-flies entering this 
room were males, while in October 60 % of them were females. 
The greatest numbers came in on October 8 (82) and 10 (96), both 
fine, but windy days. 
A great difference was noticed between the behaviour of the flies 
in the earlier and later parts of the season. Up to the middle of 
September the flies seldom remained long in the room, but numbers of 
them flew in at the garden door and almost immediately flew out again, 
often without settling. During October, however, the majority of those 
which came in remained, settling in various places for the night. 
