Tetragonula carbonaria (previously known as Trigona carbonaria) is a stingless bee, endemic to the north-east coast of Australia. Its common name is sugarbag bee. They are also occasionally referred to as bush bees. The bee is known to pollinate orchid species, such as Dendrobium lichenastrum, D. toressae, and D. speciosum. It has been identified as an insect that collects pollen from the cycad Cycas media. They are also known for their small body size, reduced wing venation, and highly developed social structure comparable to honey bees.
Tetragonula carbonaria forms honeycombs in their nests. The bee produces an edible honey; the whole nest is sometimes eaten by Indigenous Australians. The bees "mummify" invasive small hive beetles (Aethina tumida) that enter the nest by coating and immobilising the invaders in wax, resin, and mud or soil from the nest.
Stingless bees
Twenty-one genera of stingless bees (family Apidae) are described worldwide. As the name would suggest, the stings of these bees are vestigial and useless in defence. About 14 species are found in Australia, mostly in the tropical north. T. carbonaria is one of the few exceptions, in which they are found as far south as Bega in southern New South Wales. Stingless bees and honey bees are thought to have evolved from a common ancestor, like bumblebees, which would explain their similarities in social behaviour. Some of these similarities are co-operative brood care, and having different castes of queens, workers, and drones. The workers are infertile females, while the drones are males.
Taxonomy and phylogeny
The eusocial stingless bees (Apidae, Apinae, Meliponini) comprise about 374 species. Two genera occur in Australia, with Tetragonula being one of them. The Tetragonula species of Australia were once in the larger genus Trigona, but were moved into a new genus in 2013. Only minor structural differences are seen at the species level of the genus Tetragonula. T. carbonaria is nearly identical to T. hockingsi, besides a few differences in their nest architecture.
Description
Bees
Compared to other stingless bees, T. carbonaria tends to be medium-sized. However, their size can vary based on location. For instance, T. carbonaria from Queensland can be as small as T. mellipes, but in New South Wales, they can get as large as T. hockingsi. They are all predominantly black-bodied, covered in microscopic hairs. The adult workers and males are all black, with some brownish tint in certain areas such as the legs. The worker’s body length is and the wing length (including tegula) is . The male drones have very similar bodies and wing lengths, but can be identified by different antennae. T. carbonaria is a very strong flier, being able to fly up to . However, the species will not fly any further than they have to, so close resources are preferred over those farther away. T. carbonaria and its closely related species have high levels of morphological similarities. Also very low genetic variation exists within T. carbonaria. T. carbonaria can be distinguished from other species of Australian Native Stingless Bees by their brood (in a distinctive spiral unique to the species), and by the entrance (these bees tend to daub resins around their entrances, where as other species, such as T. hockingsi generally keep their entrances clean.
Nest structure
The entrance and surrounding areas of their nest are coated with a smooth, thick layer of black, red, or yellow cerumen or propolis, a material formed by mixing beeswax (a glandular secretion of worker bees) with resin (collected from plants). They lack external entrance tunnels, but do build internal entrance tunnels where guard bees patrol, looking out for any intruders (including Small Hive Beetle, Phorid Fly, and other bees). T. carbonaria builds brood cells arranged in combs or semicombs. The cells are a single layer of hexagonal combs that are built in a distinctive spiral. They are vertically elongated and in a regular vertical orientation. They are built out of brown cerumen, and house the eggs and larvae. New cells are added to the brood by the advancing front. The nest cavity may be sealed off from adjoining cavities by a hard bitumen layer of cerumen or field-collected material. The brood chamber is centred in the hive, which makes T. carbonaria suitable for hive propagation. The brood chamber is also made up of multiple horizontal layers which allow for easy division of the brood comb.