Canadian Forest Service Publications

Intra- and interspecific host discrimination by host-seeking larvae of coleopteran parasitoids. 1999. Royer, L.; Fournet, S.; Brunel, E.; Boivin, G. Oecologia 118: 59-68.

Year: 1999

Issued by: Atlantic Forestry Centre

Catalog ID: 6156

Language: English

Availability: Order paper copy (free)

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Abstract

Intraspecific host discrimation is widespread in solitary parasitoids whose adult females forage for and evaluate host suitability, whereas interspecific discrimination is less common. In some parasitoid species, mostly Diptera and Coleoptera, the larva perfomrs the last step of host searching. It has been suggested that host discrimination will rarely occur in such host-seeking larvae because their low mobility results in a low host encounter rate. We determined the extent to which the larvae of Aleochara bilineata Ghyllenhal (Coleoptera: Staphylinidae), a solitary parasioid of aggregated Diptera pupae: (1) discriminated between unparasitized hosts and hosts parasitized by conspecifics; (2) used semiochemical cues to discriminate; (3) were influenced by life expectancy, presence of conspecifics and host availability in their host acceptance decision; and the extent to which (4) A. bilineata and A. bipustularia L. a species exploiting the same hosts and occurring sympatrically, showed interspecific host discrimination. A. bilineata larvae were able to discriminate between unparasitized hosts and hosts parasitized by conspecifics in a choice experiment. Such behaviro has never previously been described for a coleopteran parasitoid or for a parasitoid species whose larvae perform host searching. Host discrimination in this species was not based on the presence of visual or tactile cues (e.g., entrance holes) but rather on chemical cues. The life expectancy of A. bilineata larvae was significanlty shorter in the presence than in absence of hosts, and older larave had lower parasitism success than young larvae in a 24-h experiment. However, the host acceptance decision of A. bilineata larvae was not influenced by larval age or the presence of conspecifics when the ratio of hosts per larva was greater than or equal to 1. When hosts were scarce, the degree of superparasitism increased significantly with the number of foraging conspecifics and the age of the larvae. Both species of Aleochara showed intra- and inter-specific host discrimination in a choice experiment. In contrast to A. bipustularia, A. bilineata larvae more frequently parasitized hosts parasitized by A. bipustularia than those parasitized by conspecifics. We suggest that host discrimination will be frequent in solitary parasitoids with host-seeking larvae when hosts are aggregated.