Influence of host developmental stage on the foraging behavior and effectiveness of the pincer wasp Gonatopus chilensis

Abstract

Gonatopus chilensis (Olmi) (Hymenoptera: Dryinidae) is a host-feeding parasitoid of delphacid planthoppers (Hemiptera: Auchenorrhyncha) with economic importance for maize crops. Several factors, including host acceptance, suitability, and defenses, significantly influence parasitoid–host dynamics and, consequently, the efficacy of parasitoids as biological control agents. Many biological attributes and traits of dryinids in general, and G. chilensis in particular, remain largely unexplored. This study aimed to evaluate the foraging behavior and effectiveness of G. chilensis and to identify biological factors influencing its performance when using the planthopper Delphacodes sitarea Remes Lenicov & Tesón (Hemiptera: Delphacidae) as hosts. Freechoice and non-choice tests conducted under laboratory conditions revealed that female G. chilensis could forage on host individuals ranging from the first nymphal instar to females of D. sitarea. Notably, the nymphal developmental stage of the host significantly impacted parasitoid effectiveness. Female parasitoids predominantly engaged in host feeding on small nymphs but preferred oviposition on larger nymphs and females. Furthermore, the size and likely the fitness of female parasitoid offspring increased with the instar or stage of the parasitized host. These findings suggest that the biological traits and effectiveness of G. chilensis are directly influenced by the developmental stage of the D. sitarea host.