In a remaining wood of the "mato grosso goiano" (Goiânia, Go, Brazil), Drosophila melanogaster marked flies as well as "white" mutants were released at the inter-section of two orthogonal axis. Traps were disposed at intervals of 20m over these axis. Every half hour, from 08:30 to 17:00, periodics collects were performed to study the dispersion of the flies in natural environement as well as to infer about the significance of the genetic component in this dispersion. The obtained data suggest the following conclusions: acitve dispersion was detected; this active dispersion is genotype dependent (it was bigger in the wild type than the " white" mutante); the dispersion patterns changed according to time; a presumiblemobility potential of 120m/hour was detected; an approximate estimate of the population density suggest values of about 25,000 flies/3,600m² for the melanogaster group and about 50,000 flies 3,600m² for Drosophila in general; the frequence of capture changed during the period.