Influence of climate regime on clover root weevil adult survival and physiology.

Clover root weevil adults collected from the field were held in four contrasting temperature, moisture and feeding regimes for a period of 10 weeks. Temperature was the main factor, inducing changes in adult wing muscle development and egg production. Egg production from females held in the ‘moist winter’ regime (10 °C, 8:16 h light:dark, moist conditions, ample food) increased linearly with time, with 90% of females fully reproductive at 10 weeks. In contrast, when held in the ‘hot drought’ regime (20 °C 16:8 h light:dark, dry conditions, intermittent food), the oviposition rate decreased logarithmically, with 32% of females fully reproductive at 10 weeks. Overall, adult mortality was lower in the ‘moist’ regimes (17%) than the ‘drought’ regimes (29%). Wing muscle development differed between regimes, ranging from 4% of adults with fully developed wing muscles in the ‘moist winter’ regime to 35% in the ‘hot drought’ regime. Clover root weevils are likely to oviposit throughout winter in most of New Zealand, but warm, dry summers will prevent a summer larval generation.