At first glance, humans no longer seem to have much in common with our ape ancestors, but what about other species that diverged at a similar time? How much do Asian honeybees (Apis cerana) and their European counterparts (Apis mellifera) have in common after 2 million years of independent evolution? Ming-Xian Yang from Rhodes University, South Africa, and Yunnan Agricultural University, China, explains that despite having completely different appearances – Asian honeybees are much smaller than European honeybees – and strategies for preventing their nests from overheating, the insects are still able to communicate through their waggle dances and can even live together harmoniously in hives. Intrigued by the bees' unexpected ability to cooperate, Yang and his colleagues Ken Tan, Sarah Radloff and H. Randall Hepburn decided to find out whether mixed colonies of Asian and European honeybees could successfully construct honeycombs together (p. 1659).

According to Yang, honeybees build comb following a specific construction strategy. ‘In a dark hive there is no leader and no blueprint for them to follow. Every bee has to perform by herself and I wanted to see if one species could collaborate with another,’ explains Yang. Travelling to Thailand to work with Mananya Phiancharoen from King Mongkut's University of Technology Thonburi, Yang took combs packed with Asian bee pupae and placed them in European hives headed by a European queen, while introducing European pupae to Asian hives, to produce mixed colonies when the adults emerged. Then he tested how the mixed colonies and unmixed colonies responded to waxes produced by both species.

The European bees were not troubled by the Asian bees' wax. They were happy to extend combs made from either species' wax and the mixed colonies were also able to extend combs made from either Asian or European wax. And when the team analysed the size of the hexagonal comb cells, they found that the European and mixed hives increased the size of cells added to Asian bee comb to the larger European size. However, the Asian bees seemed to be much more sensitive. In hives occupied by Asian bees alone, they would not extend combs made from either wax. The European bees seemed to be more adaptable than the Asian bees and in mixed hives they were also able to get the sensitive Asian bees to build comb under circumstances where they would not have done so if left to their own devices.

But how were the mixed colony workers organising themselves to construct their hybrid combs? Yang gently extracted a honeycomb from a mixed hive and filmed the insects as they worked. According to Yang, natural comb-building honeybees form bridge-like chains that other worker bees stand upon as they apply new wax to cell foundations. Amazingly, when Yang looked at the strings of bees on the combs in mixed hives, he saw bees of both species contributing to the chains and comb construction.

The bees were cooperating regardless of their differences. Despite 2 million years of independent evolution, European and Asian bees still build honeycombs using the same strategy that was originally handed down by their ancestors.

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Comb construction in mixed-species colonies of honeybees, Apis cerana and Apis mellifera
J. Exp. Biol.