Thief workers and variation in nestmate recognition behavior in a ponerineant, Ectatomma ruidum

Our findings give new insight into the relationship between nestmate recogn ition and cleptobiosis, intraspecific thievery of newly collected food item s, in a neotropical ponerine ant, Ectatomma ruidum. The expression of discr imination of nestmates from non-nestmates varied among local aggregations o ff. ruidum in a population at Barro Colorado Island, Panama. This result is due to differences in the behavior of the guard ants among aggregations, r ather than differences in the expression of recognition cues by ants. Baiti ng experiments show that E. ruidum colonies in Panama have a greater tenden cy to have overlapping home ranges than a similar population in Costa Pica. The pattern of cleptdbiosis, however, is strikingly similar between the Pa namanian and Costa Pican populations.