Abstract
Behavioral tactics play a crucial role in the evolution of species and are likely to be found in host-parasitoid interactions where host quality may differ between host developmental stages. We investigated foraging decisions, parasitism and related fitness in a gregarious ectoparasitoid, Sclerodermus harmandi in relation to two distinct host developmental stages: larvae and pupae. Two colonies of parasitoids were reared on larvae of Monochamus alternatus and Saperda populnea (Cerambycidae: Lamiinae). Paired-choice and non-choice experiments were used to evaluate the preference and performance of S. harmandi on larvae and pupae of the two species. Foraging decisions and offspring fitness-related consequences of S. harmandi led to the selection of the most profitable host stage for parasitoid development. Adult females from the two colonies oviposited more quickly on pupae as compared to larvae of M. alternatus. Subsequently, their offspring development time was faster and they gained higher body weight on the pupal hosts. This study demonstrates optimal foraging of intraspecific détente that can occur during host-parasitoid interactions, of which the quality of the parasitism (highest fitness benefit and profitability) is related to the host developmental stage utilized. We conclude that S. harmandi is able to perfectly discriminate among host species or stages in a manner that maximizes its offspring fitness. The results indicated that foraging potential of adults may not be driven by its maternal effects, also induced flexibly with encountering prior host quality.
Highlights
All insect parasitoids face the problem of finding sufficient highquality resources for growth, maintenance and reproduction
One of the optimal patterns to emerge from previous studies on the life history strategies of parasitoids is that large body size confers greater fitness [6] and closely correlates with the stage of the host at parasitism [9,10]
Behavioral response to host stage When the host stages were exposed simultaneously to S. harmandi females from M. alternatus and S. populnea colonies (Ma colony and Sp colony), significant preferences were detected in the selection of two stages (Fig. 1)
Summary
All insect parasitoids face the problem of finding sufficient highquality resources for growth, maintenance and reproduction. When foraging in a heterogeneous environment, parasitoids often encounter a variety of host species at different developmental stages. These hosts may differ in body size, behavioral defense, physiological and immunological status [1,2,3]. Optimal foraging strategy in host selection decisions by parasitoids may be determined by changes in host resources or quality [4,5]. One of the optimal patterns to emerge from previous studies on the life history strategies of parasitoids is that large body size confers greater fitness [6] and closely correlates with the stage of the host at parasitism [9,10]
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