European earwigs, Forficula auricularia L., are thought to use an aggregation pheromone but there is controversy about its source. Hence I investigated whether each developmental stage and sex produce and respond to this pheromone and what are its components. Laboratory experiments revealed that females, males and nymphs produce and respond to an airborne aggregation pheromone. Candidate pheromone components obtained from all potential sources were analyzed by gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometry. A complex synthetic blend (SB) of 30 candidate pheromone components, including benzoquinones, acids, hydroquinone, vanillin, aldehydes, ketones and an acetal significantly arrested females and nymphs in laboratory experiments. In both laboratory and field experiments, the SB lacking benzoquinones elicited significant behavioral responses from nymphs, but not from adults, suggesting that adults, unlike nymphs, use an aggregation pheromone with benzoquinones as constituent components. Additional experiments are required to determine all essential components of the earwig aggregation pheromon
