PROCTODONE, AN INSECT DEVELOPMENTAL HORMONE

¹ Department of Entomology, University of Wisconsin, Madison 6, Wisconsin

1. Diapause development in larvae of the European corn borer, Ostrinia nubilalis, was shown to be dependent on a physiological factor originating in the seventh and eighth abdominal segments.

2. Under conditions of an experimentally accelerated diapause development schedule (long-day photoperiod plus ammonium acetate treatment), the action of the abdominal system was required for about two days, the brain system for about five days, and the prothoracic system for about six days, in order to complete diapause and prepupal postdiapause development.

3. The influence of the abdominal system was shown to be transmitted by the blood stream, rather than via, the ventral nerve cord.

4. The abdominal system was postulated to elaborate and release a hormone whose physiological action is to stimulate the neuroendocrine system of the brain.

5. Because the abdominal system hormone was found to originate in the epithelial cells of the anterior portion of the hindgut, it was named proctodone.

6. Proctodone production was found to be on a 24-hour rhythmic basis, with hormone release occurring during the light hours of the photoperiod.

7. Proctodone is postulated to play a role in nondiapause growth polymorphism, periodism, and the several forms of diapause.