Make love not war: a common arthropod defence compound as sex pheromone inthe forest cockchafer Melolontha hippocastani

Mate finding in the forest cockchafer, Melolontha hippocastani, occurs duri ng a spectacular swarming period at dusk. The swarming flights are mainly p erformed by males whereas most of the females stay within the host trees an d continue feeding. Males orientate towards damage-induced green leaf volat iles (GLV) allowing location of mechanically damaged foliage. In order to d istinguish between unspecific leaf damage and damage caused by feeding fema les, male cockchafers orientate by a sex attractant. Here we show this comp ound to be 1,4-benzoquinone, which has been known for more than 40 years as a highly effective defence compound used by numerous arthropod species to repel enemies. 1,4-benzoquinone synergistically in creased the number of ma les caught in GLV-baited funnel traps during the swarming period. Significa ntly more males landed on wire cages baited with a combination of 1,4-benzo quinone and GLV than on cages baited with only GLV. The results suggest tha t the sex pheromone of M. hippocastani might have evolved from a primary ro le as a defence compound.