Nesting of Ceratina nigrolabiata, a biparental bee.

Biparental care is very rare in insects, and it was well-documented in only one bee species to this date - Ceratina nigrolabiata. However, biparental care was only recently discovered in this species, and detailed description of natural history of this species is missing. Here, we describe the nesting cycle of C. nigrolabiata. Pairs of C. nigrolabiata are established before female starts offspring provisioning. After provisioning is finished (when youngest offspring reached larval stage), the male abandons the nest. Males which are present in nests where female already finished provisioning brood cells, are probably mainly temporary visitors. The female can perform long-time offspring guarding, but only 22% of completely provisioned nests are guarded by a female. Most nests (54%) are closed and abandoned, when provisioning is completed, and other (24%) are orphaned before provisioning is finished. Guarded nests have statistically higher number of brood cells provisioned than unguarded nests. Generally, C. nigrolabiata is unique among bees due to its biparental behavior, but it has also uncommon traits of nesting biology among Ceratina bees, e.g. fast offspring development in comparison with provisioning rate, and high proportion of nests which are closed and abandoned by mother.