THE INFLUENCE OF PUPAL AGE ON SENSITIVITY TO RADIATION

T. confusum exposed to germicidal UV at any time during the 5-day pupal period exhibits a high incidence of gross morphological deformities, particularly of the wings, in the emerging adult, although the greatest sensitivity to this effect occurs on the first day of pupation. Mortality within two weeks is by far the greatest, however, if UV-irradiation is performed on the third day of pupation. By contrast, sensitivity to both lethality and abnormality-induction after x-ray exposure is greatest on the first day of pupation and declines progressively there-after, with the sharpest decline occurring late on the second day. These differences are partially explained by the fact that energy absorbed from x-rays is distributed rather uniformly throughout the pupa, whereas most of the UV energy is absorbed in the outermost tissue layers.