210 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12 



THE DISPERSION OF FLIES BY FLIGHT ^ 



By F. C. BisHOPP and E. W. Laake, U. S. Bureau of Entomology 

 Abstract 



Up to very recent years it has been generally held by entomologists 

 that flies are comparatively limited in the distances which they will go 

 from breeding places. Dr. Parker's work in Montana indicated that 

 the house-fly is normally migratory in habit and he succeeded in obtain- 

 ing specimens nearly two miles from the point of liberation. In 1916 

 the authors conducted some preliminary experiments in which colored 

 flies were liberated in the vicinity of packing houses and a considerable 

 number of these were recovered quite promptly in traps placed in the 

 yard of the packing establishments, a flight of about three-fifths of a 

 mile. The flies Uberated in this experiment consisted largely of blow- 

 flies of the species Chrysomyia macellaria and Phormia regina. Later 

 in the same summer a series of experiments was carried out to deter- 

 mine the distance of flight of several species of blowflies and house-flies 

 under rural conditions. The flies were liberated at a point near the 

 intersection of two roads and four traps were placed at given distances 

 in the four cardinal directions from the point of liberation. A total 

 of 1,745 colored flies were recovered in the sixteen recovery traps and 

 a considerable number of these were in the outer ring of traps which 

 was approximately three miles from the point of release. Another 

 experiment was conducted immediately following this in which the 

 traps were moved outward in the four directions to points approxi- 

 mately 2, 3, 4 and 5 miles from the point of liberation. House-flies, 

 screw-worm flies and the Anthomyid, Ophyra leucostoma,weTe recovered 

 in some of the most distant traps. 



In 1918 it was determined to make more extensive tests of the dis- 

 persion tendencies of various species of flies. The same general plan 

 was followed as in the previous experiment, four traps being set in 

 each of the cardinal directions from the point of liberation at distances 

 approximately 4|, 6, 7 and 8 miles. About 60,000 colored flies were 

 liberated, approximately 58 per cent being screw-worm flies, 39 per cent 

 house-flies and the remainder Phormia regina, Sarcophagids and other 

 species. As in previous experiments the flies in the various traps were 

 killed daily and examined carefully for marked individuals. The day fol- 

 lowing liberation a considerable number of marked house-flies and screw- 

 worm flieswere recovered in several of the traps. Even in those located 

 8 miles in each direction from the point of release, some screw-worm 

 flies were taken. Following this experiment the traps were renioved 



1 Published by permission of the chief of the Bureau of Entomology. 



