Sex-ratio and mating propensity in Drosophila biarmipes.

Mating success between purple eye colour mutant and wild type D. biarmipes was observed in Elens-Wattiaux mating chamber. Multiple-, female-, male- and no-choice techniques were used. The values of isolation estimate in different experiments are above one which provides no evidence for preferential mating between females and males of the same type. The comparison of sexual behaviour of mutant and wild flies clearly indicates that wild type males are more successful in mating than mutant males, and mutant females are more receptive than wild type females. Thus purple eye colour mutation affects mating propensity of both sexes in D. biarmipes. However, the difference in the number of matings of wild and mutant flies is highly significant in multipe- and no-choice experiments in which sex-ratio was 1:1 (equal number of males and females). But the difference is not significant when mating success was scored by female- and male-choice methods in which sex-ratio was 1:2 (one female and two males; one male:two females). Thus it is suggested that mating propensity in D. biarmipes is influenced by sex-ratio.

Effect of biotic and abiotic factors on pupation height in four species of Drosophila.

Effect of different biotic and abiotic factors such as sex, density, larval development time, moisture, temperature and light on pupation height were tested in Drosophila ananassae, D. bipectinata, D. malerkotliana and D. biarmipes which are commonly distributed in India. In the four species there are no sex differences in pupation height. Density of larvae and moisture content of food medium strongly influence pupation height. Larval development time, light and temperature also affect pupation height but there are intra- and interspecific variations in response to these factors for pupation site preference. Thus pupation site preference in these Indian species of Drosophila is influenced by various biotic and abiotic factors. The comparison of the present results with those found in other species clearly indicates that different species may vary in their response to different factors.

Effect of mutation on mating propensity in Drosophila biarmipes.

By using multiple-choice technique, mating success between purple eye colour mutant and wild type D. biarmipes was studied in an Elens-Wattiaux mating chamber. Red eyed (wild type) males were more successful in mating than mutant males. However, mutant females were more receptive than wild females. The results suggest that purple eye colour mutation affects mating propensity in D. biarmipes.