When maleLaspeyresia pomonella(L.) were exposed to 0 or 38 krad of gamma irradiation within 24 h posteclosion and caged at ages 1, 2, 3, 4, or 5 days for 24 h with a 24-h-old virgin female, a significantly higher percentage of unirradiated males passed spermatophores than did irradiated males in each age group. Also, when similar males were caged with a similar female each day for 5 successive days, the untreated males passed a significantly greater number of spermatophores.