Silk and sociability

The structure of the silk is essentially identical across the species of social insects that Sutherland and her team have looked at.

It also appears that there is an evolutionary link between the coiled coil silk produced by these insects and their social nature. The coiled coil silks evolved around 155 million years ago and are very tough and stable compared with the classical sheet silks.

"In the group of insects that includes ants and bees, silk arose at the time that sociality arose," she says.

"This silk is more stable and allows them to build communal hives or nests that last longer."

It is therefore probable that the evolution of the coiled coil silks has underpinned the success of the social Hymenoptera, the order of insects which contains the groups being looked at by Sutherland and her team.

Sutherland is also keen to stress that this research into bee and ant silks opens the door to a whole new way of producing materials and fibres. She says there is currently no control over the individual building blocks, such as those from petrochemical sources, when chemical synthesis is used to make different materials and fibres.

"In transgenic systems we can control the building blocks at every amino acid in the sequence. The protein sequence is encoded by DNA, which is like a book on how to make it. Using modern molecular biology, we can develop smart materials and precisely control existing matter."

The silk research is part of a joint CSIRO and Grains Research & Development Corporation Crop Biofactories Initiative.

Thermal regulation

Honeybee larvae produce silk to reinforce the wax cells in which they pupate, bulldog ant larvae spin solitary cocoons for protection during pupation, bumblebee larvae spin cocoons within wax hives which are reused to store pollen and honey, and weaver (or green) ants use their larvae as 'tools' to fasten fresh plant leaves together to form large communal nests.

"Green ants no longer make a cocoon, they have large communal nests and are completely protected in the nest," Sutherland says.

``Bees still have individual cocoons, each generation weaves another layer of silk, which helps the wax keep its structure and also keeps the hive at the right temperature. So the silk contributes to the thermal regulation and mechanical strength of the hive."