FemaleTrogoderma granarium pupae, 0–96 h old, were treated with precocene-I at 6 h intervals. Reduction in the vitellogenic oocyte number was observed in adults after precocene treatment at specific ages. Precocene-I was effective when applied to 6, 18, 30, 42, 54 and 90 h old pupae while in 0, 12, 24, 36, 48, 60, 66, 72, 78, 84 and 96 h old pupae this compound was not significantly effective. Corpus allatum activity is a major contributory factor towards precocene susceptibility. The results suggest that pupae at different ages exhibit periodic changes in corpus allatum activity that might be related to cycles of development in the reproductive system.