Research Items

Abstract

THE DISPERSION OF FLIES BY FLIGHT.—A definite knowledge of this subject is of importance in measures of control or repression. It is also of significance in the study of the spread of fly-borne diseases. Messrs. Bishopp and Laake (Journ. Agric. Research, xxi. No. 10, Aug. 15, 1921) have conducted an extensive series of observations with several species of common flies, using an estimated total number of 234,000 specimens in the experiments. These were marked by being liberated into bags containing finely powdered red chalk or paint pigment, and afterwards allowed to escape. In order to ascertain the distance of dissemination, baited fly-traps were set at measured distances, in different directions, from the point of liberation. The experiments carried out show that under rural and urban conditions flies have marked powers of diffusion; similar results obtain for both the sexes, although in very different proportions in different species. The common house fly, Musca domestica, was recaptured at a distance of more than 13 miles from the point of liberation, Chrysomya macellaria 15 miles, and Phormia regina nearly 11 miles. The fact that many favourable feeding and breeding grounds were passed over by the flies appears to indicate that, in so far as the above three species are concerned, very evident migratory habits are noticeable. The authors conclude that, under natural conditions, the influence of moderate winds on dissemination is not of great importance. The speed of flight is evidently considerable; thus Phormia regina was recovered about 11 miles away in less than 48 hours after release, and Musca domestica travelled over 6 miles in less than 24 hours. The stimuli affecting dispersion appear to be so blended and mixed as to make it impossible to judge their relative importance.