Influence Of Pre-Adult Learning On Adult’s Host Selection Of Aphidius Gifuensis (Hymenoptera: Aphidiidae)

The host-searching ability ofparasitoid depends on its response to chemical cues from the hosts and the host plants. This response may be considerably affected by genetic components, and learning processes may also play a significant role by enabling insects to adapt to changes throughout their life-cycle. Olfactory learning may occur at different stages of insect ontogeny, includingpre-adult stages. There are three different viewpoints about the specific stage of pre-adult learning:(1) the larval can learn from its environment and that this memory may be transferred from pre-imaginal stage to the adult(‘Hopkin’s host selection principle’, which belongs to natal habitat preference induction orNHPI);(2) olfactory learning occurs at adult emergence whenparasitoids contact with olfactory cues which are absorbed during the larval stage of the parasitoid(chemical legacy hypotheses); and(3) potential olfactory preference for volatiles from host aphids-infestedis established during prepupal development and was subsequently activated by exposure to the same volatiles at adult emergence.In this research, I demonstrated the stage that the pre-adult learning occurred and the manipulationto the learning behaviorof the female Aphidius gifuensis Ashmaed(Hymenoptera: Aphidiidae) that were reared onMyzus persicae Sulzer and Sitobion avenae using pepper and wheat as the host plants, respectively. The main findings were as follows:1.Whether the female parasitoid had complete pre-adult experience or not, they showed significantlypreference to host aphid-infested plants over clean air. The female parasitoid with complete pre-adult experience preferred the hosts that were contacted during the pre-adult stage,whereasthose without pre-adult experience had no preference.2.The selectivity of M. persicae-reared female parasitoids without domesticated experience on the S. avenae–infested wheat plants were significantly different with those havingdomesticated experience during one or two key developmental stages on the S. avenae–infested wheat plants. However, there was no difference between the selectivity of female parasitoids with domesticated experience during one key developmental stage and those with domesticated experience during two developmental stages on the S. avenae–infested wheat plants. The selectivity of S. avenae-reared female parasitoids without domesticated experience on the M. persicae–infested pepper plants was differentfrom those with domesticated experience during the larval stage, adult emergence, or the larval and adult emergence stages of the parasitoidon the M. persicae–infested pepper plants. However, theresults showed no difference in the selectivity of female parasitoids reared on S. avenae with domesticated experience during the larval stage of the parasitoidon the M. persicae–infested pepper plants and those with domesticated experience during the adult emergence stage or the larval and adult emergence stage of the parasitoidon the M. persicae–infested pepper plants.3.The parasitism choiceof the female parasitoidsto wheat + S. avenae and pepper + M. Persicae was concductedwith four different treatments: M. persicae-reared parasitoids without domesticated,M. persicae-reared parasitoids with domesticated experience during the larval stage of the parasitoid on the S. avenae-infested wheat plants, M. persicae-reared parasitoids with domesticated experience during the adult emergence stage of the parasitoidon the S. avenae-infested wheat plants and M. persicae-reared parasitoids with domesticated experience during the larval and adult emergence stage of the parasitoidon the S. avenae-infested wheat plants. The proportion of S. avenae parasitized by the parasitoids from the four treatments were 25.0%, 48.5%, 70.8% and 58.7%, respectively, and there were significant difference among them. The parasitism choice was conducted with female parasitoids from the four treatments: S. avenae-reared parasitoids without domesticated, S. avenae-reared parasitiods with domesticated experience during the larval stage of the parasitoidon the M. persicae-infested pepper plants, S. avenae-reared parasitoids with domesticated experience during the adult emergence stage of the parasitoidon the M. persicae-infested pepper plants and S. avenae-reared parasitoids with domesticated experience during the larval and adult emergence stage of the parasitoidon the M. persicae-infested pepper plants. The proportion of M. persicae parasitized by parasitoids from the four treatments were 54.0%, 46.8%, 63.0% and 57.1%, but there were no difference among them.Overall, our results indicated that pre-adult experience of the parasitoid adultshad influence on the habitat selection of adults. The parasitoids with domesticated experience during larval or adult emergence stage had little effect on their habitat preference. However, the habitat selection by adults was affected by the domesticated experience during the larval and adult emergence stages of the parasitoid adults. Moreover, the pre-adult learning behavior was manipulated. It could be used to increase the probability of host selected by A. gifuensis so as to enhance the parasitism to the the pest aphids.