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By Root 1215 0

programmable to store food as are bees. But they don’t live in a hive appropriate for making and storing honey. Kinglets diversify their options by being partial migrants, and animals that may have to leave their summer digs don’t lay up huge food stockpiles. Finally, as the birds travel in flocks with other birds that also feed on insects, caching might be a waste of energy, because a stockpile would be pilfered by other birds in the flock. Overall, food storage is an unlikely key to explain how kinglets survive long winter nights without freezing. The answer to that mystery must thus be elsewhere.

Honey bee carrying pollen.

23

BEES’ WINTER GAMBLE

Worker honeybees flying in and out of the hive and ranging over some fifty square miles may look as though they are all independent. Yet they are as bound to one another as if they were physically joined. Honeybees (Apis mellifera) are social animals and the colony as a whole acts as a single organism and the individuals in it are subservient to the colony’s well-being. It is individually in their best genetic interest.

Of the many surprises that have been revealed in these insects over the last century, one that is almost taken for granted is the colony response of regulating its temperature. Even in winter, temperatures in the center of bee clusters remain within a degree or two of 36°C. Whether it’s -40°C outside the hive or 40°C, the bees regulate the same hive temperature. Honeybees are the only insects in the Northern Hemisphere that can and do keep themselves active and heated up throughout the northern winter. In winter, they are able to regulate their microclimate protecting themselves and their developing young. Should any one bee leave the communal group in winter, it would, like a cell taken outside an animal’s body, die almost instantly by freezing. And if by some miracle it survived the cold, starvation would inevitably kill it. Yet, if a physiologist were to isolate a single honeybee and compare it with any one individual of thousands of other bee species, he or she might not detect anything remarkable. It is only in the context of the colony that much of the marvelous is revealed.

I’ll start by considering the highlights of how the bees regulate the temperature of their collective winter cluster, which in late winter and early spring contains eggs and tender larvae. As in overwintering by flying squirrels, kinglets, and most other organisms (including us), choosing the proper shelter or nest site is a primary prerequisite. In honeybees not only must the nest space be adequate for crowds of tens of thousands; it must also be large enough to accommodate nurseries for eggs, larvae, and pupae as well as having huge storage space for a hoard of energy supplies. Choice of proper nest site is important, and when necessary when the colony divides; that choice is not left up to chance.

The colony divides in the spring or early summer when the old queen leaves or is evicted by her daughters if she does not leave voluntarily. The old queen takes with her some 10, 000–20, 000 daughter helpers. Together the old queen and her many daughters constitute a swarm, which upon leaving the parent colony does not yet have a place to go. The colony at first temporarily clusters on a branch, and from there scout bees then fly forth in search of a new home. Analogous to our own evaluations of a potential house to occupy, bees pace out the dimensions of the place and evaluate other relevant parameters. The scouts then return to the potential site repeatedly, rechecking. Gradually each bee makes a decision, and if she deems the site potentially suitable, then she leaves a scent mark there and then reports back to the swarm.

“Report back” may sound anthropomorphic or overblown. But that’s precisely what the bee does. By a series of body movements called the bee dance (a ritualized flight behavior to the potential new home or a good food source), she indicates on the surface of the swarm cluster not only the distance and direction but also an approximation of the suitability