What factors affect host choice decisions of the soybean aphid parasitoid Binodoxys communis?

It has been hypothesized that host choice behavior in parasitoids should be affected by the female parasitoids being either time- or egg-limited. Females that are limited by the time available for host location and oviposition are predicted to be more willing to accept marginally suitable hosts compared to females that are limited by their egg supply. We were interested in the extent of egg- or time limitation affecting host choice decisions by the soybean aphid parasitoid Binodoxys communis under field conditions. We addressed this question by conducting a behavioral assay using field-collected parasitoids in the summer of 2009. In no-choice tests female parasitoids of known age were exposed to either a marginally (cowpea aphid) or a highly suitable host (soybean aphid). There was no significant effect of egg load on the acceptance of marginally suitable hosts. We found no support for either egg- or time-limitation influencing host choice decisions in B. communis. However, we found that females accepting the marginally suitable host were significantly younger than those that rejected it. That is, contrary to our initial prediction females experiencing a higher risk of becoming time-limited also had a higher probability of rejecting the marginally suitable host. This indicates that oviposition experience plays a stronger role than time limitation in host choice decisions in B. communis.