An Investigation of the Coevolutionary Relationship Between Aprostocetus hagenowii (Ratzburg) (Hymenoptera: Eulophidae) and its Cockroach (Blattodea) Hosts

Abstract

Oothecal parasitoid wasps (Hymenoptera) parasitize the egg cases (oothecae) of cockroaches (Blattodea). Oothecal parasitoids must have developed numerous adaptations to locate, parasitize, and develop within their hosts, but these adaptations have not been well studied. This goal of this dissertation was to investigate the coevolutionary relationships between oothecal parasitoids and their hosts primarily through the interactions of a generalist species Aprostocetus hagenowii (Ratzeburg)(Eulophidae) and its preferred host the American cockroach Periplaneta americana (L.) (Blattidae). During behavioral assays, gravid P. americana did not react to the presence of A. hagenowii or change their oviposition behavior. Additional experiments in total darkness or light, and electroantennogram assays indicate that P. americana does not react to or cannot detect A. hagenowii by sight or olfaction. No-choice assays were used to investigate the host range of A. hagenowii, and three new host species were recorded: Blatta lateralis (Walker) (Blattidae), Neostylopyga propinqua (Shelford) (Blattidae), and Parcoblatta fulvescens (Saussure and Zehntner) (Ectobiidae). Multi-generational no-choice assays were used to determine if B. lateralis, a peridomestic pest of growing concern, could support long-term populations of A. hagenowii. Aprostocetus hagenowii fitness rapidly declined with each generation of rearing on B. lateralis oothecae, which indicates challenges for the application of A. hagenowii for the biological control of B. lateralis. Lastly, the toxicity of baited insecticidal cockroach gels was compared between A. hagenowii and P. americana. Indoxacarb (Advion) caused non-significant (P > 0.05) A. hagenowii mortality but significant (P < 0.01) P. americana mortality, indicating its compatibility for use alongside A. hagenowii. Lack of correlation between the response of A. hagenowii and P. americana also indicates that there are differences in how the two species metabolize insecticides.