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Faiiiiia caiiicularis etc. 
Without close examluation the two species under examination are 
liable to be mistaken for the same species, but such an examination will 
serve to separate them. The abdomens of both species are conical, but 
the basal segments of the abdomen of F. caiiicularis are partially 
translucent and the abdomen of F. scalaris is black overspread with 
bluish grey; the mid-tibiae of the latter species bear a distinct tubercle 
which is not found in F. caiiicularis (Fig. 3). 
Fannia canicularis L. 
{The Lesser House-fly.) 
This species (Plate VII) is the less common of the two species of flies 
found in houses. Its occurrence and frequency are, however, very variable 
and no valid explanation has been found so far in my investigations to 
account for this variability. F. canicularis is more abundant than 
M. domestica for a short time during the early part of the summer, 
usually in May and June. With the beginning of the hot weather the 
numbers of the latter increase enormously and replace the Lesser House¬ 
fly. In many cases which were observed the latter seemed to retreat in 
small numbers to the rooms'of the house not devoted to cooking and 
they may be frequently found flying in a characteristic, jerky and 
hovering manner around chandeliers, etc. in the living and bed-rooms. 
In country houses, however, they frequently occur in numbers in the 
kitchens, as an examination of fly traps and papers in such places 
indicates. 
The numerical abundance of F. canicularis in comparison with the 
abundance of M. domestica varies considerably. In a collection of nearly 
4000 flies made in different situations, such as kitchens, restaurants, 
bed-rooms, etc. in 1907, this species formed 11‘5 per cent, of the total 
number. In 1900 Howard found that in Washington, U.S.A. only 
about 1 per cent, of a collection of over 23,000 flies made in rooms 
where food was exposed were F. canicularis and over 98 per cent, were 
M. domestica. Hamer, in 1908, in collections made in kitchens and 
“ living rooms” of houses near depots for horse manure in London found 
that the percentage of F. canicularis varded from 17 per cent, to 24 per 
cent. Niven gives the results of collections made at six different 
stations in Manchester. The total number of flies caught was 8553, 
of which 8196 were if. domestica, 293 F. canicularis, and 64 were other 
species. Thus, F. canicularis constituted 3‘4 per cent, of the total fly 
population. Robertson gives the results of similar collections made in 
