Abstract
Ligature experiments were carried out on the prepupae of the black pupa strain (bivoltine) which had been kept at 20°C after the mounting (spinning) stage. The results obtained were as follows.
Ligatures of prepupae in the early stage behind the second abdominal segments resulted in the inhibition of the manifestation of the black pupal color in the posterior parts. On the other hand, when prepupae in the advanced stage were ligatured, both the anterior and posterior parts became black. These results indicated that there was a critical period in the manifestation of the black pupal color and it was from 7 to 10 hours before pupation.
When prepupae were ligatured before the critical period and then kept at 30°C instead of being kept at 20°C, both the anterior and posterior parts of ligature became normal. It was concluded that the manifestation of the black pupal color is controlled by a hormone-like factor which is produced by some organs existing in the anterior part of ligature and the function of the organs is active at low temperature but inactive at high temperature.
Experiments in which prepupae were ligatured at different segments showed that several organs which are present in the part anterior to the second abdominal segment co-operatively control the manifestation of the black pupal color.
