Effects of X-irradiation on egg hatchability, larval and pupal survival in the tobacco hornworm, Manduca sexta

The effects of X-irradiation upon Manduca sexta egg hatchability and larval survival were studied using LD₅₀'s. Radiosensitivity declined with age in developing eggs (LD₅₀ of 9.4 kR in 2.5 to 3-days eggs contrasted to 18.2 kR in 4 to 4.5-day eggs) and in larvae. The dose-response patterns obtained agree with those previously reported for other insects.The maximal (ED₀) and minimal (ED₁₀₀) X-ray exposures resulting in eclosion successes of 100% and 0%, respectively, were utilized throughout pupal-adult development as measures of radiation sensitivity. A pronounced decrease in radiosensitivity was noted through the day of eclosion (Day 0: ED₀ = 7.3 kR; ED₁₀₀ = 18.7 kR; Day 22: ED₀ = 45.0 kR, ED₁₀₀ = 105.0 kR). X-irradiation during the pupal-adult transformation was observed to inhibit eclosion without disrupting normal metamorphosis.