Dispersal and Host Finding Behaviour of Prostephanus Truncatus (Horn) (Coleoptera: Bostrichidae)

Thomas Rath

Date of Award

1997

Document Type

Dissertation

Abstract

Olfactometric studies on the stimuli involved in long-range foraging behaviour of the parasitoids Cotesia sesamiae and Dentichasmias busseolae revealed that host plant volatiles play a major role in guiding searching parasitoids to habitats that harbour their hosts. Volatiles from herbivore-injured plants were the most attractive. Sorghum was more attractive to the parasitoids than maize. Molasses grass volatiles were attractive to C. sesamiae but repellent to D. busseolae . Combining host plants and molasses grass did not have an additive effect of increasing the response of the parasitoids. Local growth conditions influenced the volatile blend produced by molasses grass grown in two different locations in Kenya, Thika and Mbita. This was manifested by their differential attractiveness to C. sesamiae . Dentichasmias busseolae did not discriminate between host species at a distance based on the volatiles released by infested host plants. Headspace analyses of volatiles emitted by uninfested and infested host plants and molasses grass grown at Thika and Mbita, revealed qualitative differences in their compositions. Infested host plants released a richer volatile blend than the uninfested host plants. Most of the compounds identified in the herbivore-injured plants were previously reported to play a role in parasitoid recruitment. Molasses grass from Thika had a number of its identified compounds that were similar to some in the blend of infested host plants. These compounds might have played a role in attracting C. sesamiae . Molasses grass from Mbita had very few compounds common to the other plants.

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