Radiosensitivity of the flesh fly, Sarcophaga bullata (Parker), throughout larval and pupal life

Larvae, prepupae and pupae of Sarcophaga bullata (Diptera, Cyclorrhapha) were exposed to 250-kVp X rays or 137 Cs gamma rays and their subsequent responses analyzed. Third instar larvae were slightly more resistant to X rays than first instars, and equally as sensitive as prepupae and pupae through the fourth day of pupal life. Thereafter, the radioresistance of pupae increased sharply, reaching a maximum on day 9 following puparium formation. Prepupae and young pupae were compared with respect to their response (${\rm LD}_{50}/\text{emergence}$) to 250-kVp X rays and 137 Cs gamma rays; the average RBE for these radiations at this end point was found to be 0.69, the X rays being more efficient. All responses to radiation that were investigated may be associated with cell division and migration and the degree of differentiation at the time of irradiation. Overall pupal radiosensitivity remains constant during breakdown of larval tissues and reformation and restructuring of adult tissues, and then decreases progressively during differentiation and maturation of adult tissues.