Reproductive conflict between laying workers in the ant Aphaenogaster senilis

Abstract

Since workers of the ant Aphaenogaster senilis can lay male eggs, reproductive conflict may occur between these workers. We examined the occurrence of worker conflicts in groups of workers either with or without the queen. Intranidal aggression was observed in each nest for 10 min each day, and the immatures produced were counted once a week for two months. Pairs of workers involved in aggression were taken regularly from each nest and used for chemical, morphological and anatomical analyses. The attacker and the attacked workers differed in their cuticular hydrocarbon profiles. The attacker and the attacked ants were at the same middle-aged fertile stage. The attacker ant was significantly larger and more fertile than the attacked ant, and more mature physiologically (poison gland was darker). There was apparently no stable hierarchy between laying workers. In the first weeks under queenless conditions, most eggs and larvae were destroyed, but they were later reared to obtain males. The intranidal worker aggression in this highly evolved ant is discussed in relation to dominance and worker policing.