Trichogrammatids: Behavioural Ecology

Abstract

Host selection by trichogrammatid egg parasitoids is mainly facilitated by infochemicals and includes host-habitat location and host acceptance. Host egg size, shape, colour and architecture seem to play an important role in oviposition performance by Trichogramma species. Change in the rearing medium of the larval stage of the factitious host Corcyra cephalonica can significantly affect the laboratory oviposition by T. chilonis. In addition, the age and cold storage treatment of host eggs are important factors in mass rearing of trichogrammatids, which is based on the physical and chemical stimuli emitted by host eggs. The searching ability of the progeny adults is found to differ with the host insect on which they were reared. Trichogramma appears to be more habitat specific than host specific. Kairomones tend to play a role in host location and host acceptance behaviour of trichogrammatids. Genotypes of crops (e.g. cotton, rice, tomato) elicit varying response in T. chilonis for parasitising the host eggs laid on them. Intercropping is found to affect host density and parasitism levels. Significant differences in host egg oviposition have also been found, when eggs are sprayed with the extracts of different host plants. Synomonal effect due to tricosane, heneicosane, pentacosane and hexacosane is found to influence host egg parasitisation by Trichogramma. Future research may focus on extending the behaviour studies to more egg parasitoid species, host plants, host insect-parasitoid interactions at different trophic levels and to identify and utilise more of kairomones synomones.