FECUNDITY AND LONGEVITY OF DIAPETIMORPHA INTROITA (CRESSON) (HYMENOPTERA: ICHNEUMONIDAE) REARED ON ARTIFICIAL DIETS: EFFECTS OF A LIPID EXTRACT FROM HOST PUPAE AND CULTURE MEDIA CONDITIONED WITH AN INSECT CELL LINE

Abstract

Diapetimorpha introita (Cresson) (Hymenoptera: Ichneumonidae) is a native ectoparasitoid of Spodoptera spp. pupae. This parasitoid has been reared in the laboratory on an artificial diet devoid of any insect host components. However, wasps reared on this artificial diet had reduced fecundity. Efforts to increase fecundity included supplementing the diet with cell culture media conditioned with a cell line from ovaries of the fall armyworm, S. frugiperda, in one experiment and fortifying the diet with lipids extracted from pupae of S. frugiperda in a second experiment. In the first experiment, differences in mean oviposition and mean longevity among females reared on the artificial control diet (artificial diet), cell line-supplemented diet (Sf9Cell), and natural host (Host) were not significant. However, during the first 10 days of oviposition, Sf9Cell-reared females oviposited at a rate similar to the Host-reared parasitoids and at a rate faster than artificial-diet reared females. In the second experiment, females reared on the diet with added host lipid (host lipid) laid significantly more eggs than females on the artificial diet, however, longevity was not significantly affected by diet treatment. We conclude that total egg production by D. introita was improved on artificial diet supplemented with lipids from the natural host but was not increased by the addition of materials produced by an ovarial cell line derived from S. frugiperda. Future research efforts should focus on increasing fecundity of wasps reared on the artificial diet by identifying the lipid(s) or lipid-soluble material in the host pupal extract that is responsible for enhancing egg production in D. introita females.