ELIMINATION OF SEXUAL BROOD IN THE ARGENTINE ANT LINEPITHEMA HUMILE -QUEEN EFFECT AND BROOD RECOGNITION

Mated queens of the ant Linepithema humile (Iridomyrmex humilis Mayr) introduced into dequeened colony fragments rearing sexual brood elicit ed worker aggression resulting in queen larvae being bitten and elimin ated. By contrast, male larvae were spared. Regarding queen brood, kil ling mainly concerned small and medium sized larvae. A large proportio n of the large larvae escaped extermination, and prepupae and pupae we re spared. These data suggest that workers were able to discriminate s ex, caste and age of the brood. That a queen pheromone may be involved was shown by experiments using whole or cut corpses that were either rinsed or not rinsed in pentane. The pheromone eliciting worker aggres sive behaviour was shown to act over a short distance, suggesting that it is somewhat volatile. Similarities and differences between this ne w queen pheromone and other known queen pheromones acting on queen pro duction or worker attraction are discussed as well as the origin of th e signals underlying the recognition of the larval classes.