Caterpillar saliva alters scent composition of plants

Since plants are subject to insect attacks, they have developed all sorts of advanced defence mechanisms over the course of evolution. One particular defensive strategy is the release of scent particles that attract the natural predators of a harmful insect. This was found in a research carried out by Silke Allmann at the University of Amsterdam.

In a field trial with wild tobacco (Nicotiana attenuata) plants were found to be able to alter the composition of the scent emitted, after being attacked by the Tobacco Hornworm (caterpillars of the Manduca sexta moth). Through the saliva of the caterpillar the plant can 'detect' by which species it is being eaten. It then starts to release a scent that attracts one particular insect: a predatory bug that feeds on Manduca eggs and young larvae.

Source: University of Amsterdam, 2012/01/10