Effects of Larval Food-limitation on Vanessa cardui Linnaeus (Lepidoptera: Nymphalidae)

Abstract

Larval food-limitation may be an important factor influencing growth of lepidopteran populations. We tested effects of food-limitation on larval growth of Vanessa cardui Linnaeus (Lepidoptera: Nymphalidae), the painted lady butterfly. Vanessa cardui is a major pest of corn and soybeans in Iowa, making it a species of special interest. Larvae of V. cardui were reared on a commercial diet apportioned to two food-limited and one control (ad libitum) treatment, and treatments were tested in three trials with varied temperature and onset of food limitation. Trial I was conducted at 18 C and food limitation started on day 12; Trials II and III were conducted at 22 C and food limitation started on days 7 and 12, respectively. Larvae were analyzed for potential differences in both larval and adult weight and time to pupation and emergence. In Trial I, there were more days to pupation and a prolonged adult emergence in the food-limited treatments. Control larvae developed and achieved maximal weights faster than food-limited larvae. Adult weights were also significantly higher in the control. Higher temperature in Trials II and III accelerated larval development. Early onset of food limitation at this higher temperature (Trial II) exacerbated differences among treatments, whereas later onset food limitation dampened these differences.