Dietary influence of cardenolides on larval growth and development of the milkweed bug Oncopeltus fasciatus

Abstract

Larvae of the milkweed bug Oncopeltus fasciatus were reared on the seeds of eight different species of milkweed ( Asclepias), representing a wide range of cardenolide concentrations in the diet. There were few significant differences in larval developmental period, wet body weight of teneral adults, dry weight of adults, and pronotal width of adults reared on the different diets. However, the data indicate no significant correlations between cardenolide content, and body weight or size of the adult insects. There was no evidence in this study of a physiological cost or adverse effect on the larval growth and development of insects which sequestered and stored differing quantities of cardenolides. Instead, the data support a recently-proposed model of cardenolide sequestration which may be energy-independent. The validity of evidence supporting a physiological cost hypothesis for sequestration of cardenolides by the monarch butterfly is discussed in the light of these findings.