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It has been shown that many natural enemies of herbivorous arthropods use herbivore induced plant volatiles (HIPVs) to locate their prey. Herbivores can also exploit cues emitted by plants infested with heterospecifics or conspecifics. A study was conducted to test whether green bean HIPVs as well as odours emitted directly by spider mites influenced the orientation behaviour of the predatory mirid bug, Macrolophus caliginosus and its prey, Tetranychus urticae in a Y-tube olfactometer. Our results show that both spider mites and M. caliginosus preferred spider mite infested green bean plants to uninfested plants. For M. caliginosus this response was mediated by HIPVs whereas for T. urticae it was mediated through a composite response to both HIPVs and odours emitted directly by the conspecifics (and their associated products). The results may be of use in practical biocontrol situations, through e.g., plant breeding for improved HIPV production, conditioning of mass-reared predators to appropriate cues, and employment of "push-pull-strategies" by using HIPVs.

The polyphagous western flower thrips, Frankliniella occidentalis, is a severe pest of horticultural crops. Individuals from a laboratory population adapted to bean plants were transferred to new host plants, sweet pepper and chrysanthemum, to establish two new populations. The thrips appeared to perform poorly on the new host plants, as the total protein content of individual adults was lowered in the new populations. The specific activities of two insect detoxification enzyme systems, esterases and glutathione S-transferases, were assayed in vitro in the three populations. Host plant shifts had no effect on the level of general esterase activity to α-naphthyl acetate and only a minor effect on the level of glutathione S-transferase activity to 1-chloro-2,4-dinitrobenzene. The new population on pepper plants had slightly lowered glutathione S-transferase activity. The level of tolerance to the insecticide, methiocarb, was not affected by culturing the thrips on new host plants, nor was the total activity per individual of acetylcholinesterase, the target-site enzyme for methiocarb., (2000 FRAME.)