Extract from The South Australian Naturalist 87(2): 70–74. 70 The South Australian Naturalist Vol. 87, No. 2 DISTRIBUTION OF THE NATIVE SOUTH AUSTRALIAN BEE EXONEURELLA TRIDENTATA IN WESTERN MYALL (ACACIA PAPYROCARPA) WOODLANDS. Rebecca M. Dew and Michael P. Schwarz School of Biological Sciences, Flinders University, Bedford Park, Adelaide Email: rebecca.rmd@hotmail.com; michael.schwarz@flinders.edu.au INTRODUCTION: Australia has the most unusual bee fauna in the world (Michener 1965), but the nesting biology and behaviour of our bees has been studied for only a very small proportion of species. The only Australian native bees that live in hives are the stingless bees (tribe Meliponini) and these are restricted to the northern half of Australia. Most native bees are solitary nesting and live in the ground or in dead branches and stems. However, one group of native bees, the allodapines (tribe Allodapini), display varying forms of sociality and this group has been widely used to understand how insect social behaviour has evolved (Schwarz et al. 2007). Most allodapine bees have simple forms of social behaviour and lack true queen and worker castes, but there is one exception that is beginning to attract international attention. Exoneurella tridentata is an allodapine that lives in semi-arid Western Myall woodlands in the mid-north of South Australia. This species is unique among the allodapines in that it is the only species to demonstrate the most extreme form of insect sociality, eusociality (Houston 1977; Hurst 2001), which involves large colony sizes with distinct queen and worker castes. Queens in this species are much larger than workers, with widened head and mandibles and greatly enlarged and distally splayed abdomens (Fig. 1). The species may form colonies of up to 60 or more individuals, far greater than any other allodapine bee (Dew et al. 2012). Exoneurella tridentata is important for two reasons. Firstly, it provides an opportunity to understand how complex sociality can evolve from simple forms of sociality. Secondly it is one of the few native bee species in South Australia whose foraging activity extends throughout the year. Few South Australian native bee species are active during winter, and most are only active outside of the nest for short periods of one to a few months, remaining dormant for the rest of the year. Bees are the main pollinators in ecosystems worldwide, with many plants relying on bees for pollination to occur (Winfree et al. 2011). Because E. tridentata is active all year round, without a dormant period, it could play a vital role in providing pollination services for those plant Fig. 1: Exoneurella tridentata worker (A) and queen (B).