Sexual competion of irradiated males of the cowpea weevil, callosobruchus maculatus (F.)

When unmated males of Callosobruchus maculatus were irradiated with 7.5 or 10 Krad and confined with normal females, 97.90 and 89.32%, respectively, of the eggs did not hatch, compared with 15.49% infertility of the control eggs. Increasing the dose to 12.5 or 15 Krad induced 99.44 and 100%, respectively, sterility in the irradiated (I) males. When males treated with 7.5, 10 or 12.5 Krad were confined with unirradiated (U) males and females (1:1:1 ratio), infertility of the resulting eggs were 60.06, 67.96 and 69.04%, respectively. The competitiveness values of irradiated males with the above doses and ratio were 1.2, 1.6 and 1.8. Thus, males treated with substerilizing doses (7.5, 10 or 12.5 Krad) competed favourably with (U) males, and males treated with the sterilizing dose (15 Krad) were also fully competitive with (U) males. These results indicated that irradiation with 15 Krad, a sterilizing dose, did not decrease sexual competitiveness of irradiated males. (author)