Egg mass structure of the processionary caterpillar Ochrogaster lunifer (Lepidoptera: Notodontidae): is the outer egg layer sacrificed for attack by the egg parasitoid Anastatus fuligispina (Hymenoptera: Chalcidoidea: Eupelmidae)?

Abstract

Each life stage of an insect faces the challenge of various mortality factors. Through experimental and observational studies, we use those mortality agents to our advantage to control outbreaks of pest insects. The processionary caterpillar Ochrogaster lunifer Herrich-Schäffer, 1855, is a widespread native moth in Australia that defoliates host trees and causes medical problems in humans and animals. Anastatus fuligispina (Girault 1939) is an egg parasitoid described from eggs of O. lunifer in eastern Australia nearly 80 years ago for which few life history traits are known. This is the first study to investigate the life history of A. fuligispina, factors associated with parasitism levels in O. lunifer egg masses and its impacts on egg mortality. We found that parasitism level was related to the total number of eggs in an O. lunifer egg mass, with higher parasitism occurring in masses with fewer eggs. The inaccessible physical structure of the O. lunifer egg mass by layering and encasing eggs with other eggs and the searching efficiency of the parasitoid are possible key factors. Other variables such as exposure time in the field, host tree species and number of undeveloped eggs in the egg mass did not affect the level of parasitism. Further investigations on the life history of A. fuligispina may open possibilities for its application in controlling O. lunifer populations.