The Biology of Szelenyiopria talitae (Hymenoptera: Diapriidae): Larval Parasitoid of the Leaf-Cutting Ant Acromyrmex subterraneus (Hymenoptera: Formicidae)

Abstract

The biology of a koinobiont parasitoid of leaf-cutting ant larvae, Szelenyiopria talitae (Hymenoptera: Diapriidae), was studied from naturally infested Acromyrmex subterraneus (Hymenoptera: Formicidae) nests. Nests were collected in the field from the Atlantic rainforest biome in the state of Rio de Janeiro. A total of fifty-three nests were collected from 2015 to 2018. Parasitized nests were only found during the months of September and October. Approximately 22% of the nests collected over a four-year period were found to have been parasitized by S. talitae. The mean within-nest parasitism rate was 66.3%. This diapriid displayed both solitary (14%) and gregarious parasitism (86%), with up to a maximum of 12 parasitoids developing within a single host. Gregarious parasitism with two (29%) or three (21%) S. talitae per host was most frequently observed. There was a positive correlation between the number of parasitoids per host and host size (dry weight), indicating that S. talitae females oviposited a higher number of eggs in larger hosts. There was also a negative correlation between S. talitae pharate adult size and the number of parasitoids per host, which could have been caused by sibling competition for limited host resources. The high levels of parasitism seen here had a debilitating effect on the colonies. Acromyrmex subterraneus is a serious pest in Brazil, and these studies lay the foundation for understanding the impact of S. talitae on ant populations.