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  • Publication
    Métadonnées seulement
    The role of plant volatiles in host location by the specialist parasitoid Microplitis croceipes Cresson (Braconidae: Hymenoptera)
    (1993)
    McCall, Philip J
    ;
    ;
    Lewis, W Joe
    ;
    Tumlinson, James H
    A study was conducted to determine the primary source of volatile cues within the plant-host complex used by host-seeking free-flying female Microplitis croceipes Cresson in flight tunnel bioassays. In single-source and two-choice tests, using wasps given an oviposition experience on either cotton (Gossypium hirsutum) or cowpea (Vigna unguiculata) seedlings damaged by com earworm (CEW; Helicoverpa zea Boddie), the damaged seedlings were significantly more attractive than the CEW frass, which was in turn more attractive than the larvae themselves. In a series of two-choice wind-tunnel tests, the discriminatory ability of the wasps was examined, following various oviposition experiences. Significantly more wasps flew to plants with ''old '' damage than to plants with ''fresh '' damage, regardless of whether they had experience on fresh or old damage. In a comparison of plant species, wasps with only one experience on either host-damaged cotton or host-damaged cowpea were unable to distinguish between them, and showed no preference for either plant, whereas wasps with multiple experiences on a particular plant preferentially flew to that plant in the choice test. In comparing hosts with nonhosts, wasps successfully learned to distinguish CEW from beet armyworm (BAW, Spodoptera exigua) on cotton but were unable to distinguish CEW from either BAW or cabbage looper (Trichoplusia ni) on cowpea. The results show the important role played by plant volatiles in the location of hosts by M. croceipes and indicate the wasps' limitations in discriminating criminating among the various odors. The ecological advantages and disadvantages of this behavior are discussed.
  • Publication
    Métadonnées seulement
    Larval-damaged plants - source of volatile synomones that guide the parasitoid cotesia-marginiventris to the microhabitat of its hosts
    (1991) ;
    Tumlinson, James H
    ;
    Eller, Fred J
    ;
    Lewis, W Joe
    Single and dual choice tests in a flight tunnel revealed that plants damaged by host larvae are the main source of the volatiles that attract females of the parasitoid Cotesia marginiventris (Cresson) to the microhabitat of its hosts. Frass and host larvae, the other two major components of a complete plant-host complex, were significantly less attractive than the damaged seedlings; frass alone was more attractive than larvae alone. However, a recombination of larvae with the damaged seedlings was significantly more attractive than the damaged leaves alone, or damaged leaves with frass. This was due to the additional feeding damage done by the larvae. The role of plants in the host-finding behaviour of parasitoids is discussed.