Species: Tetragonula carbonaria
Synonym: Trigona carbonaria
Common names: Native stingless bee, Sugarbag Bee, Sweat Bee
Another very common bee visitor to the Commelina flowers was Trigona carbonaria. As discussed in my earlier notes it is one of a small number of species of native stingless bees that live in a communal hive structure with a queen, workers and drones. There are at least a dozen nests of this species in the reserve. The bee shown in this photo must have just started its task of nectar and pollen gathering because the corbiculae (pollen baskets) on its rear legs appear to be empty.
These bees build their nest, typically within a hollow tree although alternatives are used, from a mixture of tree resin and beeswax. The nest consists of a supporting and sealing structure at the top and bottom made from the resin/beeswax mixture. The nest contains separate, more or less spherical, pots for the storage of pollen and honey and a brood chamber of small roughly spherical cells where the queen lays her eggs. A small amount of pollen and honey is placed in each brood cell before the queen lays her egg and then the cell is sealed by the workers. The egg hatches and the larva eats the food within the brood cell before spinning a tiny cocoon within the brood cell in which it pupates before emerging as an adult bee. The queen lays a small number of unfertilised eggs that develop into male bees (drones). In addition there are a small number of somewhat larger brood cells around the outside of the brood chamber and the eggs laid in these cells develop into queen bees. Thus the colony will always have reserve queens available if something should happen to the fertile queen. By this means a colony can survive for decades even though the original queen may have died many years ago.
With European honey bees, the splitting of a hive to develop a new colony is a fairly traumatic process with the old fertile queen being taken by a swarm of workers to a new location where a nest is then constructed. When the native stingless bees decide they want to establish a new nest the workers spend weeks and even months preparing the new site and equipping it with stores of honey and pollen. When it is ready a virgin queen flies off with a number of the workers and males. After her mating flight she settles down to the task of laying eggs in her new nest. She will never fly again. It is reported that the workers from the old nest may even continue for some time to assist in the early development of the daughter colony.
There are at least half a dozen (but probably many more) nests of our native stingless bee, Trigona carbonaria, in the Reserve. This year the bees have been particularly active in collecting the resin that accompanies the seeds of Corymbia torelliana (Cadaghi). When the bees collect the resin they often inadvertently collect a seed that sticks to the resin they have collected and is taken back to the nest with them. The bees then dispose of the unwanted seeds by sticking them to the outside of their nests. The bees use the resin mixed with wax to manufacture cells for storing honey and raising their larvae. The photo shows a nest that is now covered on the outside with Corymbia torelliana seeds. Corymbia torelliana is a native of Northern Australia and was planted extensively in Brisbane in the 1970s but is now generally considered to be a weed species in Brisbane. It has been reported that the resin from the Corymbia torelliana can pose a problem for the bees because it has a lower melting or softening point than the resin from other local native trees that the bees naturally used. In very hot conditions this can cause the interior of the nest to collapse. The seeds stuck to the nests are still viable and many will be dislodged and germinate around the tree containing the nest. So if you see a patch of Corymbia torelliania seedlings look for a Trigona carbonaria nest. As far as I know there is only one Corymbia torelliania tree left in the Reserve and it isn’t yet old enough to flower and I don’t expect it will ever get the chance. However there are dozens of large Cadaghi trees in the properties surrounding the Reserve.
I found this native bee’s nest (Trigona carbonaria) when I cut away the thick Cat’s Claw vines covering an old gnarled yellow pear-fruit tree (Mischocarpus pyriformis).These native bees are stingless, unlike the European honey bees which have nested elsewhere in an old dead tree on the site. The nest has been built in a wound on the trunk that appears to have been made by an axe many decades ago. Who chopped into this tree and why they did it is a complete mystery to me. I believe this majestic old tree is the parent of the myriad small yellow pear-fruit trees growing in the vicinity.