BEHAVIORAL SPECIALIZATION IN PRE-REPRODUCTIVE COLONIES OF THE ALLODAPINE BEE EXONEURA-BICOLOR (HYMENOPTERA, ANTHOPHORIDAE)

Exoneura bicolor is a univoltine allodapine bee common in montane fore sts of southern Australia, where it exhibits a semisocial/quasisocial colony organization. Within-nest behaviour in post-emergence autumn ne sts of Exoneura bicolor was recorded with the aim of studying behaviou ral specialization in pre-reproductive colonies. Ten complete colonies were transferred to purpose-built observation nests shortly before br ood eclosion in late summer. Behaviour within observation nests was re corded for periods of up to 44 days after establishment, covering a pe riod when colonies are preparing for overwintering. Dispersal of femal es and brood rearing do not occur at this time, although some females may become inseminated. Analyses of data using multivariate techniques indicated four distinguishable behavioural castes, designated here as Guards, Nest Absenters, Nest Modifiers and Non-recruits. This represe nts a higher degree of behavioural specialization than recorded to dat e for other allodapines. Behaviours performed by Guards and Nest Absen ters are likely to involve considerable risks, but benefit the colony as a whole, so that some nestmates in prereproductive colonies exhibit altruism that frequently aids adult siblings or cousins. The males in our study were fed by females via trophallaxis and two of the males p articipated in nest maintenance tasks. Our results suggest that autumn colonies of E. bicolor form well-integrated behavioural units even th ough brood rearing does not commence until the following spring.