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item Riddick, Eric

Submitted to: BioControl
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2004
Publication Date: 2/1/2005
Citation: Riddick, E.W. 2005. Egg load of lab-cultured anaphes iole and effects of mate presence and exposure time on load depletion. Biocontrol.

Interpretive Summary: Fairyflies represent a family of parasitic wasps that commonly deposit their eggs inside the eggs of other insects. Some species, such as Anaphes iole, serve as important natural enemies of plant bugs, especially the western tarnished plant bug, Lygus hesperus. Research is underway to discover efficient techniques for mass propagating A.iole for releases in the field or greenhouse. I conducted experiments in the laboratory to determine how many eggs that adult female wasps had within their ovaries and whether or not egg number was related to female body size and age. I also determined if the presence of male wasps (mates) and the time that female wasps were exposed to potential hosts affected the rate that females exhausted their store of eggs. The results revealed that female body size and age did not have any effect on egg number. Also, the presence of mates and exposure time had no impact on the rate that females exhausted their store of eggs. Females exhausted most of their egg store within one day. This study suggests that female wasps might have their greatest propagation potential during the first few days of exposure to hosts. This study is of value to scientists (in universities, government service and private industry) that are interested in rearing and using natural enemies to control crop pests.

Technical Abstract: Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. Ongoing research is assessing the production potential of lab-cultured A.iole, using Lygus hesperus Knight as host. In this study, I tested these hypotheses: (1) egg load of virgin females was related to body size and affected by female age, and (2) mate presence and time that females were exposed to host patches affected egg load depletion. Initial egg load was 48 mature eggs and no immature eggs were detected in the ovarioles of dissected females. Egg load was neither related to body size (hind tibia or forewing length) nor affected significantly by age (0, 1 or 2d old honey-fed females). Mate presence (females with or without males) and exposure time (1, 3 or 5d on the same host patch) had no effect on egg load depletion; females exhausted most of their egg load within 1d. Females contained less than six mature eggs after 1, 3 or 5d of exposure to host patches. The results of this study suggest that A. iole females are primarily pro-ovigenic, but might be capable of generating additional eggs within a few days on host patches. Initial egg load may more closely reflect host quality rather than parasitoid body size or age. Since mated and unmated females deplete most of their egg load in 24h, progeny production might be greatest during this time period of exposure to suitable hosts.