Intraspecific competition and performance of Anagrus virlai parasitizing the corn leafhopper

Abstract

Intraspecific competition and avoidance of superparasitism are critical for biologicalcontrol. In this study, we conducted behavioural and biological trials to assess intraspecificcompetition in the egg parasitoid Anagrus virlai, targeting the corn leafhopperDalbulus maidis. Firstly, we investigated whether A. virlai can distinguish betweenunparasitized and parasitized host eggs using long-range cues in an olfactometerexperiment. Secondly, we evaluated whether A. virlai parasitism and emergenceunder varying host densities are affected by the presence of multiple conspecificwasps foraging within the same host patch. In the olfactometer test, A. virlai did notdifferentiate between corn leaves with parasitized and unparasitized eggs. Regardingthe parasitoid's performance, the number and percentage of parasitized eggs wereinfluenced by the density of females foraging simultaneously in the same host patch.Significant increases in collective parasitism were observed when two or more parasitoidswere present in each arena. Competitive interaction did not affect wasp emergence,and A. virlai proved to be a solitary species. Moreover, the negativerelationship between per-capita parasitism and the number of conspecific wasps perarena demonstrated mutual interference among parasitoids. These findings highlightthe impact of competitive interactions on A. virlai performance and suggest a potentialaggregated response of the parasitoid to high-density patches of hosts.