Winter World_ The Ingenuity of Animal Survival - Bernd Heinrich [112]
Any nest search involves numerous scouts, and it usually continues until several scouts have each found potential shelters. Since the whole colony must stay together and thus can go to only one nest site, the next obvious problem is that of achieving a consensus on the best site after several are indicated. The queen does not make that decision. She has nothing to do with it. She is a follower. Unanimity is reached, instead, first because different scouts check out each other’s finds, and secondly because they readily convert if they encounter a better nest site than the one they themselves had found. However, consensus, without the aid of individual intelligence, is reached mainly because the scouts advertising inferior sites stop dancing, while the best sites are advertised more strongly; each potential nest site is advertised honestly according to its relative worth.
A swarm that has left the hive may hang at its temporary home on the branch for hours or days while scouts search for a nest site. During this time the swarm maintains its cluster core temperature near 34° to 36°C, but its cluster-mantle temperature is barely above 15°C (Heinrich 1981). All of the bees on the mantle are too cold to be able to fly, until they warm up by shivering, which costs much energy. The low mantle temperature helps to conserve the swarm’s energy supplies, which is critical especially during all of this time they are house-hunting. But how do the mantle bees know when to shiver and get ready to fly? A recent study gives us the answer.
Honeybees’ nests were once man’s only source of sugar, and humans have maintained an active interest in these insects for this reason alone for thousands of years, as judged by cave paintings, and possibly for millions of years as judged by our sweet tooth and inventiveness to satisfy it. Since early in the last century the bee’s inestimable value as pollinators, both in agro-and wild ecosystems, has boosted our perceptions of their lives and their ways even more. With all of the interest and nonstop research on honeybees for over a century, especially that brought to the attention of the whole world by the spectacular discoveries of the dance language by the Austrian Nobel laureate Karl von Frisch and his numerous students and their students and associates and recruits, one would think that the well of discoveries in them would by now be dry.
Not so. Every discovery sets the stage for the next. While von Frisch disclosed to us their stunning dance language as well as their sensory world, neurobiologist Randolf Menzel at the Free University of Berlin deciphered the connections of the bee’s senses with their short-and long-term memories. In recent decades we have discovered the mechanisms of how they regulate their individual body temperatures, and how they communally regulate their swarm temperature. Cornell biologist Thomas D. Seeley elucidated how scout bees evaluate the suitability of a potential nest site, which I alluded to previously, and only last year (2001) he with Jürgen Tautz, a colleague from the Theodor-Boveri Institute in Germany, discovered and documented an acoustical “piping” signal bees make by contractions of the flight muscles that is mechanically much like their shivering. Scout bees giving those signals stimulate cool bees on the outermost layers of a swarm cluster to shiver and warm up. Like the bee dance, which can be interpreted as an abstract or greatly abbreviated enactment of a flight toward the intended location, the piping signal similarly symbolizes preflight warm-up. As in a warm-up, the sound (vibration) frequency in any one piping sequence