Open-Air Nesting Swarms

Open-air bee colonies are honey bee colonies that build their nests in the open, on tree branches, rock overhangs or building eaves, rather than inside a cavity or hive. Asia's giant honey bees (Apis dorsata, Apis laboriosa) and dwarf honey bees (Apis florea, Apis andreniformis) naturally live this way; our honey bee (Apis mellifera), on the other hand, builds in the open only in swarms that fail to find a suitable cavity, and in hot climates. This page explains how open nests work and what a beekeeper should do on coming across such a colony.

The difference between open nests and cavity nests

Honey bees (genus Apis) fall into two groups according to how they build their nests:

In open-nesting species there is no wall protecting the comb. This job is taken on by the bee curtain, which covers the surface of the comb in several layers: the bees regulate temperature, block rain and sun, and act as a shield against predators.

The giant honey bee (Apis dorsata)

It is widespread in the forests and farmland of South and South-East Asia. It builds a single comb, which can exceed a metre in width, on the branches of tall trees, on cliffs, water towers and building eaves. Dozens of colonies can be found together on the same tree.

• Shimmering defence: when a wasp approaches, the bees in the curtain raise and lower their abdomens in sequence, creating a "wave" across the surface; this defence confuses the predator and drives it away.
• Strong defence: when disturbed, it can attack with large numbers of bees; approaching the nest is dangerous.
• Migration: colonies migrate long distances with the seasons, following the flowering.
• Natural host of Tropilaelaps: Tropilaelaps mites, a major threat in beekeeping, are originally parasites of this species; they later jumped to our honey bee.

Its cliff-nesting close relative, the Himalayan giant honey bee (A. laboriosa), lives under the overhangs of steep rocks in high mountains (see Himalayan honey bees).

Dwarf honey bees (Apis florea and A. andreniformis)

The red dwarf honey bee (A. florea) ranges from Oman and Iran to Pakistan, India and South-East Asia. It builds a single palm-sized comb on shrub and tree branches. The upper part of the comb wraps around the branch, and honey is stored there, in the thick section around the branch.

• Ant barrier: it smears sticky bands of resin on both sides of the comb's branch to stop ants from reaching the nest.
• Horizontal dance floor: it communicates the location of forage by dancing on the horizontal surface on top of the comb, pointing directly at the source.
• Gentleness: it generally stings very little; the small colonies move easily.
• Invasive spread: it has moved outside its natural range via human transport: it was recorded in Sudan (Khartoum) in 1985 and spread south along the Nile from there; in 2007 it was seen in the Jordanian city of Aqaba. It is also found in Iraq, Israel and Saudi Arabia.

The black dwarf honey bee (A. andreniformis) is smaller and darker; it lives hidden among dense branches in the forests of South-East Asia.

Why does our honey bee sometimes nest in the open?

The honey bee (A. mellifera) normally seeks a cavity. When a swarm leaves the parent hive, it first clusters on a branch; scout bees wait a few hours or a few days until they find a suitable space. If no suitable site is found, or the weather turns bad, the cluster may start building comb where it is. That is how an open-air colony forms.

• In temperate climates: a colony in the open may get through the summer but mostly dies in its first winter; cold, wind and rain break up the bee curtain over the comb.
• In hot climates: in regions such as Africa, northern Australia or California, open colonies can survive for years.
• Semi-open sites: rock crevices, wide tree hollows and the underside of eaves provide partial protection.

What should you do if you find a bee colony in the open?

1. Identify it first: a newly settled cluster with no visible comb is a swarm and can be collected easily. If comb has been built, the colony has settled in; moving it takes more work.
2. Safety: wear full protective equipment; take care with ladder safety on high branches and eaves. Keep nearby people and animals away.
3. Don't use insecticide: insecticide poisons both the bees and the honey in the combs; other bees can rob this honey and carry the poison back to their own hives.
4. Transfer the combs to frames: cut out the brood combs, tie them into empty frames with rubber bands or string, and place them in the hive.
5. Get the queen: transfer most of the bees into the hive with a brush or a box; if the queen is inside, the others will walk into the hive.
6. Leave the hive in place until evening, then move it; do a short check the next day.
7. Health check: keep a colony of wild origin separate for a few weeks; check for varroa and brood diseases.

Honey hunting and the value of open-nesting bees

In Asia, the honey of giant and dwarf honey bees has been collected by honey hunting for centuries. In countries such as Vietnam and Indonesia there is also a traditional method of tying horizontal poles to trees to make it easier for giant honey bees to settle. Although these bees cannot be kept in hives, they are important pollinators in forests and farmland; excessive and destructive harvesting, forest loss and agricultural pesticides are reducing their numbers.