Juvenile hormone biosynthesis in diapause and nondiapause females of the adult blow fly Protophormia terraenovae.

In vitro synthetic activities of juvenile hormones (JH) were examined using a radiochemical assay in diapause females and reproductive females of the blow fly, Protophormia terraenovae. Thin layer chromatography showed that products of the corpus allatum (CA) comigrated with a synthetic sample of JH III bisepoxide but neither with JH III nor methylfarnesoate. JH synthetic activities increased in females reared under LD 18:6 at 25 degrees C, as the ovaries developed. The synthetic activities remained low in previtellogenic females reared under LD 12:12 at 20 degrees C. Removal of the pars intercerebralis completely prevented ovaries from development under reproductive conditions, and removal of the pars lateralis caused partial or full development of ovaries under diapause-inducing conditions. In these operated animals, the JH synthetic activities were not significantly different from those of the intact and sham-operated animals. The results indicate that the CA in P. terraenovae produces mainly JH III bisepoxide and a decrease in the JH production rate is a cause of diapause induction. PI neurons and PL neurons in the brain do not directly mediate changes in the JH production rate, but regulate ovarian development cooperatively with some unknown allatostatic and allatotropic factors.