Reproductive life-history traits of the classical biological control agent Hypena opulenta (Lepidoptera: Erebidae): Using agent biology to support post release monitoring and establishment

Abstract

It is important to develop efficient and cost-effective methods for monitoring the establishment and fitness of biological control agents. Understanding how simple and obtainable measurements of insects or their body parts relate to reproductive life-history traits could facilitate assessing the fitness of biological control agent populations in the field. Across many insect taxa, female size represents a principal constraint on potential fecundity. Here, we investigate the relationship between pupal measurements and aspects of potential fecundity in Hypena opulenta (Lepidoptera: Erebidae), a recently released biological control agent against Vincetoxicum rossicum and V. nigrum (Apocynaceae) in Ontario Canada. We dissected adult H. opulenta females of different ages to assess their strategy of oogenesis by counting and measuring the number of eggs in their ovarioles and establishing the relationship between pupal measurements and potential fecundity. A second experiment was conducted to determine the relationship between pupal weight and adult longevity. While moths emerged with eggs in their ovarioles, oogenesis continued throughout the adult stage, and mean egg size increased with time after emergence. These observations place the moth closer to being an income breeder on the ovigeny index scale. We observed no significant relationship between pupal weight and total number of eggs; however, pupal weight was positively correlated with adult longevity. These results demonstrate the limited use of general size-fecundity relationships in post-release assessments for insects that are income breeders. However, they also highlight how the understanding of reproductive strategy in H. opulenta can provide important information to aid in its establishment and spread at release sites.