Re-analysis of pheromone-mediated aggregation behaviour of European earwigs

Abstract Aggregation of the European earwig, Forficula auricularia L. (Dermaptera: Forficulidae), is known to be, in part, a response to aggregation pheromone. However, many aspects of pheromone biology remain unknown or controversial. In two-choice experiments with field-collected specimens in a still-air olfactometer, we determined that female, male, and juvenile F. auricularia all produce and respond to aggregation pheromone and that the pheromone is perceived by means of olfaction. Various sources (or extracts thereof) reportedly containing or emitting pheromone (including the insects’ integument, tibiae, or fecal excreta) did not induce significant responses. Our data suggest that none of these sources contains all or any of the essential pheromone components. These controversial results may be due to differences in (i) experimental procedures, such as single- or grouped-insect bioassays, or (ii) developmental stages of the bioassay insects. It is conceivable that juveniles and adults produce and respond to different components of aggregation pheromone.