Studies on the Mode of Action of the Diapause Hormone in the Silkworm, BOMBYX MORI L.,

Abstract

1. The action of the diapause hormone has been studied by injecting extracts of the heads of male moths or of the brain-suboesophageal ganglion complexes of pupae into pupae expected to produce non-diapause eggs. 2. The effect of the injection of hormone upon young oocytes is to make them develop into diapause eggs. Older oocytes, which have already acquired non-diapause characters, are not affected. 3. The hormone is almost completely inactivated when injected on the day of pupation. The hormone is most effective when injected into pupae 2-3 days old, at which stage the ovarioles have started to grow vigorously. It is ineffective 1-2 days before adult emergence, by which time all the oocytes have acquired non-diapause characters. 4. The hormone is inactivated in all pupae irrespective of whether they are destined to produce diapause eggs or non-diapause eggs. Inactivation of diapause hormone (in contrast to that of juvenile hormone) is partially relieved by exposure to low temperature or by simultaneous injection of indian ink. 5. The extracts prepared as in (1) above do not serve as a stimulant for the brain causing the suboesophageal ganglion to produce diapause hormone. The action of the extract faithfully reflects the function of the diapause hormone which originates in the suboesophageal ganglion.