Effects of diet on life-history traits in a trivoltine Kobe population of Hyphantria cunea (Drury) (Lepidoptera: Arctiidae)

Abstract

The effects of diet on life-history traits were compared among individual webworms reared on an artificial diet or the leaves of two host plants in a trivoltine population of Hyphantria cunea collected in Kobe, Japan. The lower threshold temperature for development and the thermal constant among one generation did not differ largely according to the diets. There were two variations in the larval instar numbers, those being the six- or seven-instar type. The incidence of the seven-instar type fed the artificial diet was significantly lower than those fed on the host plants. The pupal weight for the six-instar type was significantly heavier for those fed the artificial diet than those fed on the host plants. Seasonal host plant effects were detected in some developmental traits. The critical photoperiods for diapause induction at 20 and 25°C were similar between the host plants, and were shorter with the artificial diet than with the host plants. The present results suggest that the data for the artificial diet need not be modified in the parameters for the developmental rate, but that the critical photoperiod for diapause induction needs to be slightly lengthened when the data are applied to field insects.