Alarm pheromone in the earthworm Lumbricus terrestris.

Noxious stimulation of the earthworm Lumbricus terrestris elicits secretion of a mucus that is aversive to other members of the species, as well as to the stimulated animal when it is encountered later. This alarm pheromone is not readily soluble in water and retains its aversive properties for at least several months if not disturbed. Its influence may be responsible for some features of the data on instrumental learning in earthworms.