蜜蜂分巢选址有学问

House-hunting is full of decisions, for us and honey bees. One early decision we both face is where to live. P. Kirk Visscher at the University of California, Riverside, often in collaboration with Thomas Seeley at Cornell University, NY, has long been studying how honey bees make these decisions. Swarms of honey bees split off from their mother colony and go house-hunting, looking for a secure cavity（洞） in a tree or elsewhere that will make a good home for the new colony. In this process, they communicate to each other what they have found by dancing: a scout bee returning from a good site moves over and over in a figure-eight pattern that indicates the direction and the distance to the site, and other scouts read these dances and inspect the site themselves.

Usually, the swarm's scouts find more than one site, in which case the swarm faces a decision that must be made quickly since the swarm is exposed and the season for honey collection is passing. The decision, however, must also be good decision, the future welfare of the colony depending on a good home site.

Visscher, Seeley and colleagues report Dec. 8 in Science Express that they have found another, overlooked, signal that plays a role in this process -- a signal that is similar to those that occur between neurons in the brains of monkeys making decisions. Called the "stop signal," it is a very short buzz delivered by the sender scout while butting her head against the dancer. Its effect is to shorten and ultimately end the dance.

"It appears that the stop signals in bee swarms serve the same purpose as the inhibitory（禁止的） connections in the brains of monkeys deciding how to move their eyes in response to visual input," said Visscher, a professor of entomology（昆虫学） . "In one case we have bees and in the other we have neurons that suppress the activity levels of units -- dancing bees or nerve centers -- that are representing different alternatives. Bee behavior can shed some light on general issues of decision making. Bees are a lot bigger than neurons for sure, and may be easier to study!"

To study the stop signal, Seeley, Visscher, and Thomas Schlegel at Bristol University, United Kingdom, set up swarms, one at a time, on an island off the Maine coast that was devoid of（缺乏） natural nesting cavities. They also set out two identical nest boxes. They labeled scout bees visiting the two boxes with paint marks of two colors. They then video-recorded the scouts producing waggle（摆动） dances and tracked dances produced by the marked scouts with a microphone and videotape to ascertain when they received stop signals, and from which bees.

What the international team observed was that the stop signals were primarily delivered to dancers reporting a particular site by scouts that had been marked at the other site.