The Role of Spruce Monoterpene Derivatives as Oviposition Stimuli for Rhizophagus grandis , a Predator of the Bark Beetle, Dendroctonus micans

The literature provides abundant examples of secondary compounds produced by conifers, which have been turned against the trees by bark beetles. For example, toxic monoterpenes may be used by the insects as cues for host selection (see references in Moeck et al. 1981) and moreover are converted to less toxic oxygenated derivatives (e.g., Hughes 1973a, 1973b; Renwick et al. 1973), which serve as aggregation pheromones for the adult beetles or their larvae (Borden 1982, Francke and Vite 198 3). One step further along the food web, these original defensive compounds of the host-plant take another twist: bark beetle pheromones are notably used by predators and parasitoids for locating their prey or host (Vite and Francke 1976, Borden 1982).