Escalation of aggressive interactions during staged encounters in Halictusligatus say (Hymenoptera : Halictidae), with a comparison of circle tube behaviors with other halictine species

Circle tube experiments on the primitively eusocial bee, Halictus ligatus, were performed for a variety of combinations of caste and size. Push, Lunge , and Back without reverse behaviors enabled us to determine the dominant i ndividual in most comparisons. Behavioral differences were readily detected within the first 15 min except for different-size forager-forager and same -size foundress-foundress pairs, for which 30 min of observations was requi red. In same-size forager-forager pairs, no differences in behaviors betwee n individuals were detected even after 90 min, lit extended observations, d ecreases in the frequency of the mild dominant behaviors were accompanied b y a switch to the highly aggressive mandibular hold on the neck, particular ly in different-size foundress-foundress and gyne-gyne pairs. Three workers were killed by their own queen as a result of this escalation of aggressio n. We discuss caste-based differences in the circle tube setting in terms o f behaviors expected under more normal conditions and compare our data with published results from other species.