496 Observations on Habits and Parasites of Common Flies 
and stirred with a sterile platinum needle, and cultures made on the 
media mentioned with two loopfuls of the fluid. Two plums with small 
holes yielded amongst other organisms a few colonies of B. coli. Four 
with large cavities yielded numerous colonies of B. coli, hut one with 
a large hole yielded no faecal bacteria. 
It may be inferred from these few experiments and from the known 
habits of flies and wasps (p. 504) that great contamination of fruit 
hanging on trees and exposed for sale with faecal and putrefactive 
bacteria must be caused by these and other insects. 
Outdoor habits of Musca domestica. 
One of the most remarkable features of these experiments is that 
amongst the 106,978 flies caught in various traps only ten specimens 
of M. domestica occurred, two in trap VI, and eight in the trap baited 
with fruit (VII). This was not due to the absence of this species, for 
hundreds entered the house and examples were not infrequently seen 
and caught in various parts of the garden. Moreover specimens were 
very seldom seen on the carcases of large or small animals, exposed in 
various other places. 
The influence of weather on flies. 
No attempt appears to have been made hitherto to study the effects 
of different weather conditions on the habits of flies. Throughout the 
year 1915 careful notes were kept of the daily weather conditions and 
records were obtained of the velocity of the wind, of the rainfall occurring 
in the daytime and at night, of the hours of bright sunshine, and of the 
readings of thermometers placed in various situations. These meteoro¬ 
logical data have been studied in conjunction with the records of flies 
caught in various traps, and observations on “wild” flies in the garden. 
Unfortunately after June the season of 1915 was abnormally cold, 
the mean temperature in the screen in July being 2-5° F., in August 
1-3° F., in September 1-4° F. and in November 3-8° F. below the average. 
July and August were also unusually wet. 
The more important meteorological conditions affecting flies are 
first discussed, and then the combinations of these conditions which 
make up different classes of days. 
Bright sunshine. In meteorological records it is the practice to 
quote only the number of hours of bright sunshine per week. Such 
statements are of little value in considering the effects of weather on 
