Endogenous free fatty acids repel and attract Collembola.

We used video recording of the movement pattern of Protaphorura armata (Collembola) to test whether its avoidance of the odor of dead conspecifics extends to related species. P. armata was repelled by the odor of dead individuals of Onychiurus scotarius and Onychiurus circulans, but not by live individuals. Free palmitic, oleic, and linoleic acids were present in extracts of the three repellent species, but only free palmitic acid was detected in extracts of a fourth nonrepellent species, Folsomia candida. Synthetic palmitic acid was attractive to P. armata, linoleic acid was repellent, and oleic acid gave no response. o. scotarius and O. circulans also contained 2,3-dimethoxy-pyrido[2,3-b]pyrazine, known as a defense substance. We discuss the role of free fatty acids in predator avoidance, conspecifics attraction, and food recognition in P. armata.