The 24-hr rhythm of emergence of Ephestia kühniella Zell. from the pupa

Abstract

The endogenous 24-hr emergence rhythm of the moth Ephestia kühniella Zell. was unaffected by a daily variation of atmospheric pressure or humidity. Decrease in temperature from 30° to 25°C initiated a new rhythm of emergence; the opposite change did not affect the existing emergence rhythm. A change from light to darkness stimulated emergence; a change from darkness to light retarded it. A single decrease of temperature or change of light intensity initiated a new rhythm of emergence. A 16-hr periodicity of emergence was initiated by a corresponding periodicity of temperature but the rhythm reverted to a 24-hr periodicity immediately the temperature variations ceased. No 24-hr rhythm of oxygen consumption by the pupa in uniform conditions could be detected. The time between peak periods of emergence appeared to increase when pupae were kept in constant conditions in a gas mixture containing 7 per cent oxygen. The endogenous emergence rhythm was displaced by about 12 hr after pupae had been kept at 0·5°C for 12 hr.