Influence of Temperature on the Termination of Diapause in the Egg of Pryeria sinica MOORE (Lepidoptera: Zygaenidae)

Abstract

We have known that the Pryeria sinica MOORE are the important defoliator to the Euonymus japonica THUNB. as majior garden plants in Japan.
The appearance of the adult of P. sinica is one time in a year and it falls on the season from the last ten day of October to the middle of November. The egg mass are laid around the tip of stem. The overwintering of this species take place in the stage of egg and the hatching is observed at the beginning part of March of the next year after the laps of a resting state.
In this paper there are presented the results of experiments performed to cold required for completing the diapause in the eggs of P. sinica in Tokyo. The results obtained are summarized as follows:
The optimal constant temperature for the completion of diapause development lies between 2.5 and 15°C, and the upper threshold temperature are about 20°C, respectively.
In fields, the eggs deposited in the beginning of November complete the diapause development by the beginning of January of the next year. Therefore, the eggs of P. sinica hibernate in a state of growth arrested by low temperature during the winter.
The diapause-terminated eggs hatched normaly at any temperature ranging from 7.5 to 22.5°C.