Influence of temperature on oviposition, quiescence, and mortality ofRhinocyllus conicusFroelich, a thistle head weevil, was investigated at different constant temperatures ranging from 15 to 36°C. Mean fecundity varied from a low of 6.6 eggs per female at 15°C to 123.6 eggs per female at 22.5°C. Fecundity was more or less constant in the range 19.5–36°C. Overwintering adults began oviposition in response to increased temperature and presence of musk thistle,Carduus thoermeriWeinmann, buds. These features of oviposition suggest an adaptation ofR. conicusfor synchrony with its weed host, musk thistle. Mortality, measured as cumulative 50% mortality, at the different temperatures was compared between sexes; males had a shorter life span than females, and both sexes had shorter lives at higher temperatures.