The changes in quantities and qualities of Delta-steroids, and especially ecdysteroids, in adult female Zyleborus ferrugineus with age, and stage of the reproductive cycle at each age, under different treatments are being determined by combined radioimmunoassay and HFLC. The beetle requires a dietary Delta7-sterol to mature, and thus mean rates of loss of locomotor vigor and reproductive capability with age and mean longevity of adult females provided only dietary cholesterol versus 7-dehydrocholesterol will be correlated with changes in Delta7-steroids in the entire insect, and in selected organs, e.g., ovaries. We seek to determine whether loss of locomotor vigor and fertility, and time of death can be correlated with the titer of Delta7-steroids falling below demonstrable thresholdsin the insect.