TEMPERATURE-DEPENDENT WINTER SURVIVAL OF BEMBIDION-LAMPROS AND TACHYPORUS-HYPNORUM

Wintering survival of the predatory beetles Bembidion lampros and Tach yporus hypnorum was tested under held conditions with manipulated peri ods of constant frost, Survival of both species was influenced negativ ely by short frost periods during an otherwise mild winter. Exposure t o 2 weeks of frost during a mild winter reduced survival below 10%, Su rvival during a harsh winter with constant subzero temperature was hig h for both species, Overwintering survival was also tested experimenta lly under different temperature regimes in the laboratory, Survival of B. lampros at fluctuating temperatures between -2 degrees C and +6 de grees C, was lower when the temperature fluctuated on a weekly basis t han on a daily basis, Survival of T. hypnorum was severely affected by fluctuating temperatures around 0 degrees C independent of the freque ncy. Winter survival was generally higher for B. lampros than T, hypno rum under equivalent temperature conditions both in the field and in t he laboratory, Super cooling point (SCP) and weight changes were measu red on individual specimens during overwintering under field condition s, SCP for B, lampros decreased as the winter became harsher while SCP for T, hypnorum seemed to be constant under the same conditions, At t he end of the winter SCP for B, lampros increased dramatically, Weight changes of individual specimens were constantly low for both species during a harsh winter, Mean weight changes of B. lampros and T, hypnor um during overwintering was followed under different temperature regim es, Mean weight changes after the winter did generally not explain win ter mortality. Copyright (C) 1996 Elsevier Science Ltd