Enemy specification in the alarm-recruitment system of an ant

Many kinds of ants use odor trails to recruit nestmates to food discoveries and new sites; minor workers of the myrmicine Pheidole dentata also use them to recruit major workers ("soldiers") to the vicinity of intruders. This newly discovered alarm-recruitment system has proved to be narrowly specific. Only fire ants and other members of the genus Solenopsis, which include some of the potentially most dangerous enemies of Pheidole, have been found to evoke the response when present as single scouts or small invading forces. The glandular source of the Pheidole trail pheromone and the cues by which Pheidole recognize Solenopsis have been experimentally determined.