At Phoenix, Arizona, approximately 147,000 radioactive Musca domestica were liberated at a primary release site. For the 2-day period following, 15 fly traps were operated at 3 secondary sites 0.5 mile from the primary release point; the flies collected at each secondary site were then dusted with a characteristic dye, after which they were again liberated.
Collection stations within one mile of the primary release point indicated that, even though fly dispersion from that site followed a general random design, one sector of the recovery zone yielded a higher rate of recapture of radioactive specimens than the remaining sectors.
A total of 104 radioactive and dyed M. domestica was retrieved. Fly movement from each of the 3 secondary release sites exhibited a random pattern. Reciprocal migration was manifested, certain specimens reversing their initial path of migration and returning to the general area of the primary release site.
The data indicate M. domestica to be essentially an insect of migrating habits. The house fly apparently spends the greater part of its existence in moving from site to site not only in search of breeding and feeding sources but also from an inherent instinct to wander.