DISPERSAL, DENSITY AND MICRODISTRIBUTION IN DROSOPHILA-SUBOBSCURA COLLIN

Traps were used, arranged in octagonal annuli and flies were marked with micronized fluorescent dust. The flies were distributed contagiously within an annulus; males and females were distributed independently; site-preference was temporary. Traps in outer annuli attracted more flies, but made less efficient use of their attractive areas. Flies marked with different dusts did not have significantly different chances of being recaught. Flies of both sexes dispersed in an essentially random fashion. Pooled data indicate that males dispersed a mean distance of 49.3 m and a mean-square distance of 2769 m2. The corresponding female values were 36.0 m and 1750 m2. The density of the population was around 12/100 m2, of which approximately 2/3 were females. The total effective population number was approximately 10,000. The methods used here are compared with those previously used by other investigators. Future work should concentrate on inter-population migrants.