Impact of Lysiphlebus testaceipes Stage of Development within Greenbug Hosts on Survival and Development of Late-Stage Hippodamia convergens Larvae

The endoparasitic wasp Lysiphlebus testaceipes Cresson and the predator, the convergent lady beetle, Hippodamia convergens Guerin-Meneville, are part of an aphidophagous guild responsible for suppressing greenbug, Schizaphis graminum Rondani, populations on the Southern Plains of the U.S. Lady beetles consume L. testaceipes within their aphid hosts, a competition dynamic known as intraguild predation. Our objective was to examine at what stage parasitized greenbugs are a suitable food source for convergent lady beetles. Third- and 4th-instar convergent lady beetle larvae were fed limited daily numbers of greenbugs or greenbugs in three stages of parasitism by L. testaceipes. Early stage parasitism diets had little effect on H. convergens, however, compared with a greenbug diet, late-stage parasitism diets reduced ladybeetle survival as much as 54%, delayed development as long as 2.6 days, and reduced adult weight by as much as 2.3 mg (22.5%). Consumption of parasitized aphids reduced parasitoid abundance, but competition for a limited resource (greenbugs) has the potential to significantly reduce fitness of convergent lady beetles.