Evidence for a two-component external marking pheromone system in an aphid hyperparasitoid.

The megaspilidDendrocerus carpenteri (Curtis) is a solitary ectohyperparasitoid of aphid primary parasitoids. It avoids superparasitism, but the avoidance rate depends on the amount of time elapsed after the first oviposition. In addition, females discriminate in a time-dependent manner between hosts parasitized by themselves and hosts parasitized by conspecifics. They recognize parasitized hosts by means of two externally perceivable chemical markers that are deposited on the mummy shell. One of the markers is highly active, short-lived, not passable through gas chromatography (GC), and freezing sensitive; the other is moderately active, persistent, GC-passable and freezing tolerant. Using two markers is believed to be advantageous for the hyperparasitoid female, as their ratio provides information on mark age and on the producer of the mark (the female herself or a conspecific female).