Abstract
The effect of melanotic tumour formation on the survival rate of female flies was investigated for a period of five weeks after eclosion in the C-104 mutant strain of Drosophila melanogaster, found in a natural population in Budapest. Melanotic tumours developed only in female flies in the vicinity of spermathecae. The incidence of tumour formation was higher in the dead females than in the living ones. This fact explicitly indicated that tumour formation has a deleterious effect on the survival rate and thus the life span of its carriers. It also implied that non-self recognition or self-defense reaction is accomplished at the expense of the organisms. The reason for the maintenance of this melanotic tumour gene in a natural population is discussed.
