INTERSPECIFIC AGGRESSION IN COLONIES OF THE SLAVE-MAKING ANT HARPAGOXENUS-SUBLAEVIS

Colonies of the slave-making ant, Harpagoxenus sublaevis, may simultan eously contain workers of several Leptothorax slave species. We observ ed aggressive interactions among slave-makers, between slave-makers an d slaves, and among slaves in 11 mixed colonies. The first two types o f aggression appear to be correlated with reproductive competition for the production of males. Aggressive interactions among slaves, howeve r, occurred mainly between slaves belonging to different species. In t wo colonies, in which one slave species clearly outnumbered the other, the majority attacked and finally expelled all nestmates belonging to the minority species. Our observations thus suggest that in Harpagoxe nus colonies a homogeneous ''colony odor'' is not always achieved and that heterospecific slaves may occasionally be mistaken for alien ants : Gas chromatographic analyses of ants from mixed colonies similarly s how that cuticular hydrocarbon profiles may differ strongly between he terospecific nestmate slaves.