Chemical espionage by parasitic wasps : how Trichogramma species exploit moth sex pheromone systems

anglais. Interactions between insects are for a great deal mediated by semiochemicals. For instance, female moths release specific volatile chemicals in order to attract males of the same species. These substances are called sex pheromones. Egg parasitoids use various chemical cues in their search for hosts, including substances originating from the host insect. Such chemicals, of which the function is advantageous for the receiver but not for the emitter, are called kairomones. The terms pheromone and kairomone are not attached to substances themselves but to functions of substances. One and the same substance may thus function as a sex pheromone in one context and as a kairomone in a different context. This dissertation deals with egg parasitoids that use moth sex pheromones as kairomones and thus exploit their host's chemical communication system. In other words, they commit chemical espionage.In the research described here, the phenomenon of chemical espionage has been studied in two systems, each consisting of a moth and its egg parasitoid. The first includes the cabbage moth, Mamestra brassicae , a common pest on cabbage and other vegetables, and the parasitic wasp Trichogramma evanescens . These are common species in Europe and temperate Asia. The second is an American system, namely Heliothis zea , a moth with common names related to the crops on which it is a pest (e.g. cotton bollworm, corn earworm or tomato fruitworm), and its parasitoid Trichogramma pretiosum . Trichogramma species are the most widely used insects for biological control of insect pests in the world, with areas of application totalling several millions of hectares.

néerlandais; flamand. Kairomonen in de insektenwereld zijn chemische stimuli, waarvan de functie voordelig is voor de ontvanger, maar niet voor de afzender. Dit proefschrift handelt over eiparasieten, die sexferomonen van nachtvlinders als kairomonen gebruiken en zo het chemisch communicatiesysteem van hun gastheer uitbuiten. In het hier beschreven onderzoek is dit uitbuitingsverschijnsel (chemische spionage) bestudeerd aan de hand van 2 systemen, elk bestaande uit een nachtvlinder en bijbehorende eiparasiet. Het ene systeem omvat de kooluil, Mamestra brassicae, en de parasitaire wesp Trichogramma evanescens, beide algemeen voorkomend in Europa en gematigd Azie. Tevens is een Amerikaans systeem bestudeerd: de katoenmot Heliothis zea en haar parasiet Trichogramma pretiosum