Some ecological observations on houseflies in Egypt.

Observations were made over a three-year period (1949-51) on the occurrence of peaks and depressions in the housefly population of Talbia, a small village in a rural district near Cairo. The results, illustrated by eight figures, are based on counts of flies collected on wooden grids placed at selected sites.Two peaks and two depressions occur annually-in spring and autumn, and at midsummer and in winter, respectively. These fluctuations in fly population appear to be associated with changes in temperature, although a certain irregularity in the findings suggests that some other factor-such as the number of manure heaps accumulated at various times of the year-may be involved. Temperature also affects the concentration of flies at indoor and outdoor haunts; an increase above 23.5 degrees C tends to drive them indoors. There is no indication that humidity influences the density of fly populations.