Evidence of Social Nesting in the Ceratina of Borneo (Hymenoptera: Apidae)

The bee tribe Ceratinini is important for understanding early stages in social evolution. Their extant sister tribe Allodapini contains no strictly solitary species, and while some Ceratinini are commonly regarded as solitary, little behavioural data exist to substantiate this. Studies on Asian congeners have shown recurrent sociality in temperate and subtropical ranges while behavioural data are lacking in tropical regions. Field work along the west coast of Borneo in Sarawak, Malaysia, has provided some insight into these tropical taxa. Here we describe the nesting biology and social behaviour of four taxonomically described yet behaviourally unclassified Ceratina species. These four species are from three subgencra, namely Ceratina (Ceratinidia) accusator Cockerell, C (Ceratinidia) nigrolateralis Cockerell, C. (Neoceratina) dentipes Friese, C (Pithitis) smaragdula Fabricius. Nests of all species were typically attended by an adult female while all species except C accusator had a low frequency of multi-female nesting assemblages. The four tropical ceratinines described here and all other behaviourally classified species exhibit recurrent patterns of maternal care, maternal longevity, and nest protection. Prolonged parental care found across the genus and occasional transitions into sociality make Ceratina of future interest for the study of life history and social evolution.