Research press release


Nature Physics

Honeybees take the strain for the colony’s greater good


ハチは、個体よりも群れを優先させるさまざまな集団行動を示すことが知られている。セイヨウミツバチ(Alis mellifera Linnaeus)は、女王バチと一部の働きバチが、群れを離れて新たな群れを形成する分封によって、新たなコロニーを作る。その際、偵察バチが適当な営巣地を探している間、残りの群れは近くの木に集まって、主に逆円錐型のクラスターを形成する。このクラスターは、環境の変化に応答して形と密度を変え、高温や雨、風、捕食に耐えて、凝集した超個体として群れを保つ。

今回Orit Pelegたちは、ミツバチの群れがかく乱に耐える仕組み解明するため、ミツバチの円錐状のクラスターを板の下面に付け、さまざまな振幅、周波数、継続時間で振動させた。その結果、水平方向に振動させると、群れが自己組織化して、当初の円錐形より機械的に安定した扁平な構造になることが分かった。


Honeybees in resting swarms respond to physical disturbances by changing the shape of the whole swarm, even if doing so comes at an individual cost, reports a paper published online this week in Nature Physics.

Bees are known to exhibit varied collective behaviours that prioritize the group over the individual. The so-called western honeybee (Apis mellifera Linnaeus) makes new colonies by swarming, in which a queen and some of her workers leave their hive to form a new one. While scout bees search for a suitable nesting site, the rest of the swarm cluster on a nearby tree, typically in the form of an inverted cone. The shape and density of this cone alters as the swarm responds to changes in the environment - withstanding high temperatures, rain, wind and predation to stay together as a cohesive superorganism.

To understand how swarms endure disturbances, Orit Peleg and colleagues attached conical clusters of honeybees to the underside of a board, which they shook with varying amplitudes, frequencies and durations. They found that horizontal shaking causes swarms to self-organize into flatter structures that are more mechanically stable than their initial conical shape.

Using particle-based simulations, the authors show that swarms can adapt by each bee individually responding to the strain it experiences by moving in the direction of increasing strain to maximize group stability. In this way, the bees’ physical interactions achieve the long-range signalling necessary for apparent collective intelligence. This result complements the traditional idea that collective behaviours arise from interactions through local chemical cues, which seldom confer long-range effects.

doi: 10.1038/s41567-018-0262-1


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