Some Effects of Gamma Radiation and a Chemosterilant on the Mexican Bean Beetle1

Abstract

Gamma radiation or the alkylating agent apholate sterilized male and female Mexican bean beetle, Epilachna varivestis Mulsant. with adults the effect was produced with ionizing radiation at 8 or 16 kr. Pupae were more susceptible—complete sterilization of females was obtained at doses of 1, 4, 8, or 16 kr and males were sterilized at doses of 4, 8, or 16 kr. Larvae were more susceptible to direct radiation effects than pupae and pupae more susceptible than adults. Adult male or female bean beetles dipped in an aqueous solution of 0.5% apholate or confined for 48 hours on bean foliage sprayed with the same concentration in water were completely sterilized. Untreated female beetles mated with treated males (irradiated or exposed to apholate at effective doses) deposited about the same number of eggs as females of untreated pairs, but no eggs hatched. Treated female beetles (irradiated or exposed to apholate at effective doses) mated with untreated males deposited few or no eggs. Adult beetles of either sex irradiated in the pupal or adult stage or apholate treated adults were shorter lived than untreated beetles. Untreated female beetles mated first with irradiated or apholate-treated males produced sterile eggs, but a subsequent mating with untreated males resulted in the production of viable eggs.