To test the effect of sepia eye colour mutation on mating activity in D.bipectinata, experiments were conducted by using mutant and wild-type stocks and employing multiple-, female-, and no-choice techniques. Mating success in different experiments was observed in Elens-Wattiaux mating chamber for one hour. The values of isolation estimate in diffence between the numbers of homogamic and heterogamic matings is not significant, indicating random mating between wild-type and mutant files. The comparison of sexual activity of two types of flies clearly indicates that wild-type males are more successful in mating than mutant males. However, there is no differce in the sexual activity of two types of females. Thus sepia eye colour mutation diminishes the sexual activity of males in D.bipectinata which provides evidence for sexual selection. The results of mating propensity tests obtained in the experiments employing multiple-, female- and male-choice techniques are similar showing significant difference in the number of matings of the two types of males. However, the difference number of mating of the two types of males. however, the difference in the number of matings of sepia mutant and wild-type males is not significant in no-choice experiments. Thus, sexual activity is influenced by different choice situations. However, sex-ratio has no effect on the mating success in D.bipectinata.
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