FEEDING BY COLORADO POTATO BEETLE LARVAE (COLEOPTERA, CHRYSOMELIDAE) IN-FIELD CAGES - MEASUREMENTS AND A MODEL

Feeding rates of Colorado potato beetle larvae were measured in 24-h t rials in small field cages on potato leaflets that remained attached t o the plants. Four models were constructed to explain the results; the se differed by including or excluding the effect of insolative heating on larval body temperature, and by including or excluding thermoregul atory behavior, in all combinations. In all instars, observed feeding was independent of mean body temperature during the trial as estimated by each model, and less than the amount predicted using this mean to drive constant-temperature feeding rate functions. The four models wer e assessed by regressing model predictions on observed feeding rates. For first and second instars, there was no relationship between observ ed feeding and the amount predicted by any of the models, probably bec ause the feeding rate was small relative to the precision of the measu rements. Far third and fourth instars, predictions from the model that included both insolative heating and behavioral thermoregulation did not differ significantly from observations. Simulations using this mod el suggested that daily mean body temperature fails to predict foliage consumption because this mean cannot account for the effects of trans ient occurrences of suboptimal temperatures.