Of the eight existing species of honey bee, the most ancient lineage belongs to two very small species that build unique nests composed of a single comb formed around a small branch or twig.
Apis florea, the red dwarf honey bee, and A. andreniformis, the black dwarf honey bee, together constitute subgenus Micrapis, the dwarf honey bees.
Both species hail from southern and south-eastern Asia, where they often occur sympatrically, despite being quite distinct in evolutionary terms. Micrapis stings are often incapable of penetrating human skin, so these bees may be handled without the need for extensive protective equipment. Their exposed nests render them vulnerable to predation, so both species favour sites among dark and dense foliage. Despite their preference for forest habitat, dwarf honey bees are important pollinators of tropical fruits and are often hunted for their fragrant honey, which has cultural significance in some areas. The tiny colonies comprise around three thousand individuals, with a comb that measures up to approximately seventeen centimetres in diameter, and each nest yields around a mere 250 millilitres of honey.
In Vietnam, dwarf honey bees are known as ‘fly bees’ and ‘forest honey’ is a rarity that fetches high prices. Given that it has a broader distribution and is less aggressive than A. andreniformis, honey is more likely to be sourced from A. florea. In keeping with their primitive evolutionary status, dwarf honey bees perform a simplified version of the ‘waggle dance’ in which foragers point directly towards the food source they have discovered.
Apis florea, the red dwarf honey bee, has a prominent red-brown band on the abdomen, with a total body length of just 7-10 millimetres. This species is unusual in a number of respects. Red dwarf honey bees’ life cycle involves seasonal migration, and if relocating over a distance of less than 200 metres, the bees will salvage wax from the old nest to build a new one. Apis florea is the only species of honey bee known to exhibit this behaviour; although it may be prudent and economical to recycle the precious wax, this practice also carries the inherent risk of translocating pathogens.
Since their nest consists of an open and unprotected comb (although it may be hidden amongst foliage), dwarf honey bees have evolved several extraordinary strategies to combat potential predators. ‘Shimmering’ is a visual effect involving fast-moving waves, which are propagated over the surface of the nest as the bees raise their abdomens in sequential order. This is thought to intimidate predatory wasps, birds and mammals. When an individual bee perceives a threat, it may also emit an audible warning signal (this is called ‘piping’); some 0.3-0.7 seconds later, this is followed by a ‘hissing’ sound (also audible to the human ear) generated by large numbers of the bees and produced by movements of their wings. This builds to a crescendo as the ‘hissing’ spreads to the entire colony. Hissing may be used to repel mammalian predators, including bears. But the most troublesome predator for dwarf honey bees is the Asian weaver ant, Oecophylla smaragdina. Due to their diminutive size, dwarf honey bees are no match for the weaver ants in direct combat, but where these ants are prevalent the bees plaster sticky plant resins in bands around branches that lead to their nest, creating an effective barrier to obstruct the ants. Guards alert other members of the colony to the presence of ants using a specific hissing sound. Additional bees then man the barriers and more of the sticky resin is deposited to reinforce defences.
Apis andreniformis, the black dwarf honey bee, may even be fractionally smaller than A. florea in overall size, making it the smallest species of honey bee in existence. It is also darker than A. florea and is conspicuous in that the first two segments of the abdomen are black. The black dwarf honey bee is a lowland species usually found at elevations of less than one thousand metres. Nesting sites may be anywhere from one to fifteen metres above ground level, with the average height being about 2.5 metres. Apis andreniformis will also daub plant resins around the edges of the nest and along the branch upon which it is situated to act as a repellent for ants and other insects.