CONICET-Grupo de Investigación en Ecofisiología de Parasitoides, Departamento de Ecología, Genética y Evolución-Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, (CI428EHA) Ciudad de Buenos Aires, Argentina.
J Insect Sci. 2010;10:53. doi: 10.1673/031.010.5301.
Parasitoids locate inconspicuous hosts in a heterogeneous habitat using plant volatiles, some of which are induced by the hosts. Hyposoter horticola Gravenhost (Hymenoptera: Ichneumonidae) is a parasitoid of the Glanville fritillary butterfly Melitaea cinxia L. (Lepidoptera: Nymphalidae). Melitaea cinxia lays eggs in clusters on leaves of Plantago lanceolata L. (Lamiales: Plantaginaceae) and Veronica spicata L. (Lamiales: Plantaginaceae). The parasitoid oviposits into host larvae that have not yet hatched from the egg. Thus, though H. horticola is a parasitoid of Melitaea cinxia larvae, it must find host eggs on plants that have not been fed on by the larvae. Using a Y-tube olfactometer, the response of H. horticola to odors of Melitaea cinxia and extracts of the attacked plant species were tested. Three week-old eggs (near hatching) were attractive to young H. horticola, but one week-old eggs were attractive only to old or experienced H. horticola. Melitaea cinxia larvae were not attractive. A water extract of P. lanceolata was attractive, but ethanol or hexane extracts were not. None of the extracts of V. spicata were attractive. Leaves of V. spicata were attractive only if harboring eggs, but P. lanceolata leaves with eggs were not. Free flying H. horticola in a large outdoor enclosure were presented with host and plant cues. As in the olfactometer, V. spicata was attractive only when eggs were on it, and P. lanceolata was somewhat attractive with or without eggs. This study shows for the first time that a parasitoid of larvae uses egg volatiles or oviposition-induced plant volatiles, to find host larvae, and that Melitaea cinxia eggs or traces of oviposition induce the production of these volatiles by the plant. Based on the results, and given the natural distribution of the plants and M. cinxia eggs, parasitism of Melitaea cinxia eggs on P. lanceolata would be expected to be low. Instead, under natural conditions, a fraction of the eggs in virtually all egg clusters are parasitized on both plant species. The mismatch between the experimental results and the natural pattern of host-parasitoid interactions is discussed in terms of the expected coupling foraging cues with foraging success.
寄生蜂利用植物挥发物来定位不显眼的宿主，其中一些挥发物是由宿主诱导产生的。Hyposeoter horticola Gravenhost（膜翅目：Ichneumonidae）是 Glanville fritillary 蝴蝶 Melitaea cinxia L.（鳞翅目：Nymphalidae）的一种寄生蜂。Melitaea cinxia 在 Plantago lanceolata L.（Lamiales：Plantaginaceae）和 Veronica spicata L.（Lamiales：Plantaginaceae）的叶片上产卵，呈簇状。寄生蜂将卵产在尚未孵化的宿主幼虫体内。因此，虽然 H. horticola 是 Melitaea cinxia 幼虫的寄生蜂，但它必须在幼虫尚未取食的植物上找到宿主卵。使用 Y 型嗅觉仪，测试了 H. horticola 对 Melitaea cinxia 气味和受攻击植物物种提取物的反应。对即将孵化的三周龄卵（近孵化）有吸引力，但对一周龄卵仅对年老或经验丰富的 H. horticola 有吸引力。Melitaea cinxia 幼虫没有吸引力。P. lanceolata 的水提取物具有吸引力，但乙醇或己烷提取物没有吸引力。V. spicata 的提取物均无吸引力。只有当叶片上有卵时，V. spicata 的叶片才有吸引力，但没有卵的 P. lanceolata 叶片则没有吸引力。在一个大型户外围场中自由飞行的 H. horticola 被展示了宿主和植物线索。与嗅觉仪一样，只有当 V. spicata 上有卵时，它才具有吸引力，而带有或不带卵的 P. lanceolata 则具有一定吸引力。这项研究首次表明，幼虫的寄生蜂利用卵挥发物或产卵诱导的植物挥发物来寻找宿主幼虫，并且 Melitaea cinxia 卵或产卵痕迹诱导植物产生这些挥发物。基于这些结果，并且考虑到植物和 M. cinxia 卵的自然分布，预计在 P. lanceolata 上寄生 Melitaea cinxia 卵的情况会很少。相反，在自然条件下，两种植物上几乎所有卵簇中的一部分卵都会被寄生。实验结果与宿主-寄生蜂相互作用的自然模式之间的不匹配，根据预期的觅食线索与觅食成功的耦合进行了讨论。
