WITHIN-NEST BEHAVIOR IN A EUSOCIAL AUSTRALIAN ALLODAPINE BEE EXONEURA(EXONEURELLA) TRIDENTATA HOUSTON (APIDAE, XYLOCOPINAE)

Understanding the processes involved in the evolution of social behavi our has become one of the most challenging areas of modern biology. Si nce bees and wasps exhibit a variety of social organisations they are particularly useful for addressing social evolutionary questions. Allo dapine bees are especially useful for examining social evolution, sinc e species display varying forms of social organisation from solitary t o eusocial. This study examines within-nest behaviour of Exoneura (Exo neurella) trinentata, a native Australian allodapine bee. This species has the largest known colony sizes of any allodapine bee and exhibits striking size variation among female nestmates suggesting that social ity may be regarded as highly eusocial. Here we assemble a behavioural catalogue for this species and show that although many behaviours are similar to those recorded for other allodapines, this species differs by the marked presence of overt aggression displayed in the form of b iting. Overtly agonistic behaviours have not been recorded for other A ustralian allodapines and have been recorded only rarely in other allo dapine fauna. Exoneura tridentata appears to differ from other highly eusocial species where there is usually little or no aggression but in stead ''gentle despotism''.