Behavior of usurping queens in colonies of the ant species Leptothorax nylanderi (Hymenoptera: Formicidae)

Animals can reduce their costs of parental care by exploiting the behavior of unrelated conspecifics. Such 'intraspecific parasitism' has been observed in the small ant species, Leptothorax nylanderi. This study aims to identify how parasite queens of Leptothorax nylanderi are integrated into established colonies. Both in natural multi-queen colonies and in manipulated laboratory colonies, workers were temporarily aggressive towards the usurper queen, which herself remained initially passive and inconspicuous but later attacked the resident queen, the workers and the brood. Queen-queen aggression led to the elimination of one of the two queens and the restoration of monogyny. Usurpation is not associated with size polymorphism in L nylanderi.