Thermoperiodic induction of diapause in the predacious mite, Amblyseius potentillae

Abstract

The effect of temperature on the induction of diapause was studied in the phytoseiid mite Amblyseius potentillae. Photoperiodic induction of diapause was shown to be temperature dependent; at higher constant temperatures diapause incidence was virtually absent. When a photoperiod was applied in combination with a thermoperiod, diapause was induced only if the cool phase of the thermoperiod coincided with the scotophase; scotophase temperature appeared to be of much greater importance for diapause induction than photophase temperature. For the first time in a mite it was shown that diapause could be induced by a thermoperiod in continuous darkness. No diapause or only a very low incidence of diapause was found in continuous darkness when either the high, mean or low temperature of the thermoperiod was applied as a constant temperature throughout. A thermoperiodic response was found to be absent in continuous light. The thermoperiodic response curve determined for A. potentillae appeared to be closely similar to the photoperiodic response curve. Both the critical scoto- and cryophase were about 10 h in duration. Incidence of diapause was found to be dependent on the amplitude of the thermoperiod; except for the higher temperature range diapause incidence increased with increasing thermoperiod amplitude. Full induction of diapause was obtained with an amplitude of 4°C and above. No indication was found for the existence of a temperature threshold for thermoperiodic induction of diapause in A. potentillae.