Studies on the ecology of insects sterilized artificially (gamma radiation), 8

Gamma-ray irradiation of 7 KR from 137Cs on the oriental fruit fly pupae two days before emerging did not significantly reduce the percentage of emergence and longevity of adult flies. However, highly sterile adults (more than 98.9%) were found in those combinations, S#male# x N#female#, N#male# x S#female# and S#male# x S#female#. The result of observation of sperm activity in spermathecae of females mated with sterilized males showed that the sterility is caused by dominant lethalities. The sexual competitiveness between S#male# and N#male# has been examined in experiments of S#male# x N#male# x N#female#. (1) The data suggest that the sterility percentage concerning with egg hatchability is proportional to the rate of sterilized males replaced for normal males when that is expressed with a multiple of the ratio of normal males to normal females. Seven such straight lines thus obtained made us possible to find the theoretical expectation of sterility percentage. (2) Relationship between the percent egg hatch observed (y), or that estimated theoretically (Y), and logarithm of ratio, S#male#/N#male# (x) was showed to be two straight regression equations, y=18.413-11.952 (x - 1.295) and Y=11.890-15.462 (x - 1.295). Ratio of regression coefficients of the equations was 0.772. (3) Correlations between the sterility percentage and ratio, S#male#/N#male#, showed in three convex curves under three degrees of competitiveness (0.265, 0.576 and 1.001). When both the values of S#male#/N#male# in the mating experiments and the sterility percentages are given, it is possible to obtain degrees of competitiveness using the curves. (auth.)