In Australia, the spiral structured hives of Tetragonula Carbonaria, a stingless species of bee, are both fascinating and confusing scientists. The structures they create really need to be seen to believe.
What are Tetragonula Carbonaria?
The type of bee under the spotlight is one of the Melipones, a tribe of social insects that includes bumblebees and stingless bees. There are only 500 species of bees out of 20,000 with these specific features. Their speciality is the way they build their hive.
Tetragonula Carbonaria are well known for their ability in making spiral shaped hives, as you can see in this picture, published online last week. In this magnificent structure, called a brood comb, each level of the hive contains hundreds of interconnected alveoli. These spherical cells each contain an egg, a larvae or bee nymph, depending on the progress of metamorphosis. These cells are called brood cells.
A multi-stage construction
A bee has to spend about 50 days in one of these cells before reaching maturity. To build each of these cells, the bees secrete wax through their abdominal glands, which they mix with a plant resin derivative, to form a solid material called cerumen.
'Each cell is supplied by worker bees who regurgitate food up to two thirds of the hives height, a dose sufficient enough to feed the larvae until its development at the pupal stage', explains Tim Heard, the entomologist at the origin of the photo. 'The queen lays an egg on this food supply and the cell is immediately closed so that the larvae can grow in a closed environment'.
The workers move from one cell to another, moving from the inside to out and building each level of the hive over the previous one. When the queen has finished laying her eggs in the alveoli on the top floor, she goes down to the bottom of the hive, where the adults have already hatched, and starts the process again. 'This image shows only one floor of the brood comb, a fully developed nest will consist of 10 to 20 layers' says Tim Heard.
No explained cause
Researchers have tried to explain how the bees managed to build this incredible structure. Heard meanwhile, prefers to retain some mystery. 'This shape can be the result of random behaviour, or it can be adaptive. A possible advantage would be the space saving and air circulation between the layers. But then, you wonder, why don’t you see this in more species', he notes.
Another fun feature of this hive is its 'anti-enemy doormat'. Bees cover the entrance with a mixture of wax and propolis. This 'doormat' has antibacterial features that that can get rid of bees pathogens. It also deters predators like leafcutter ants from infiltrating the hive.