Workers measure only about 3–4.5 millimetres and are mostly black. Tetragonula is the most widespread genus of stingless bees in South and Southeast Asia, and its species are hard to tell apart.
They range from India and Sri Lanka through Indochina, Malaysia, Indonesia and the Philippines to New Guinea and northern and eastern Australia. Australia has about 11 species of stingless bee in two genera, six of them Tetragonula. Tetragonula carbonaria lives from Bundaberg in Queensland to the south coast of New South Wales, Tetragonula hockingsi in tropical Queensland and across the top of the Northern Territory.
They nest in tree hollows and build with cerumen, a blend of wax and resin. T. carbonaria is known for a brood comb coiled into a spiral of 10–20 tiers, surrounded by clusters of honey and pollen pots. Intruders such as beetles are entombed in a mix of resin, wax and mud.
Australians call their honey sugarbag. Aboriginal people have long gathered it from hollow trees, and used the wax to seal tools and to make didgeridoo mouthpieces. The honey is tangy and aromatic, and a University of Sydney study found it has antimicrobial properties.
Colonies are now kept in small wooden hives of about eight litres. Honey is scarce, about a kilogram a year, and is harvested only in warm regions, as elsewhere it would weaken the colony. In Malaysia and Indonesia these bees are known as kelulut, and keeping them is growing into a business.