by Marlene Zuk
Chapter 9
Six-Legged Language
The Battle between Impatience and Procrastination
SUDDENLY, a lot of bees seemed to be flying in and out of our garage. There has always been a space of about a foot between the top of the wall and the roof, so it is not an enclosed building, but while I was used to seeing insects, our cats, and the occasional possum or raccoon making use of the opening, for a couple of days a steady stream of humming golden-bodied workers went back and forth at one corner. Needless to say, no flowers grow in our garage, so I wasn't sure why I was seeing half a dozen or so bees buzzing overhead every time I went to get my bike.
I told my husband. They're just bees, he said. Don't worry about it. I wasn't worried, exactly. I just was a little leery of what the increased traffic might portend. And on the third day I noticed a baseball-sized clump of bees surrounding a beam inside the garage near the opening they had entered. Uh-oh, I thought. They're swarming.
After a suitably pointed "I told you so" to my husband, I knew just what to do. I called Kirk Visscher, who is a professor of entomology at my university and an expert on bees and beekeeping. "Help," I said. "We've got bees." Kirk drove over to our house with a portable hive constructed from boards, which he set out at what we hoped was a tempting yet suitably lengthy distance from the beam, and our garage. With a little luck, he assured us, the bees would move their operations into the hive and he could take the colony to use in his research back on campus.
Luck, however, was not with us. A day later, the clump had grown to the size of a small football, and honeycomb was visible when the layer of bees shifted. Kirk returned, this time with the age-old beekeeper's equipment of a funnel and smoker. He gently pumped the smoke over the cluster, which had no discernable effect on the bees other than to make them hum in what, at least to my ears, was a rather agitated way. I backed up into the driveway and asked Kirk exactly what we were trying to accomplish, since having a garage full of annoyed and active bees did not seem like an improvement over having one full of reasonably quiescent ones.
"We're just trying to convince them that this wasn't the great place they first thought it was," he said. Like moving to a neighborhood you later discover has bad air quality or a lousy school system, I guess, only without the complication of already having filed the paperwork and commencing escrow. Whatever the rationale, in another day the entire swarm had suddenly decamped, as if they had never been, except for the telltale irregularly shaped sheets of fragrant honeycomb attached to the beam. Presumably, the bees had left for a more permanent home, whether in a tree cavity or some other fortunate beekeeper's hive, but at any rate sufficiently far from our garage.
Honeybee swarms are the colony's way of reducing overpopulation. When a colony grows large, the worker bees nurture new queens, and the old queen, along with perhaps half of the workers, goes off to establish a new hive somewhere else. Initially, the pioneering bees and their queen settle in a mass like the one inside our garage, while scout worker bees go out and look for a new place to live. For centuries, enterprising humans have taken advantage of these temporary swarms to capture a new colony and place it into a manufactured hive, as Kirk had attempted. While handy for the beekeepers, this abrupt human-induced end to the house-hunting process had meant that no one paid attention to, or understood, the extraordinary process the bees undertake in making a decision about where to go.
Remember, the bees are in a swarm of up to ten thousand individuals, surrounding a plump, fecund queen, who must be protected at all costs. Only a few bees are able to survey their surroundings and choose a site where they and subsequent generations will spend the rest of their lives. What makes for exclusive bee real estate? How do the scouts convey the news about where they have been to everyone else in the swarm? And once the information is delivered, how does the group decide which of the prospective new homes is the most suitable? Finally, how can such an enormous group of tiny creatures stay together and get to the same place?
The answers to these questions shed light not just on the behavior of bees, but on how decisions are made by groups of animals, whether these are insects, migrating birds, or humans. At the same time, only bees and their close relatives show the kind of complex communication system that challenges our definition of what it means to be human. How do insects decide where to go? Further, and more provocative, is the means by which they indicate their destination a real language?
The Spirit of the Hive
ALL KINDS of animals, and even some microorganisms, make decisions: go left instead of right, eat this food and not that, sing now or rest for the afternoon. Decisions by female Drosophila about where to lay their eggs have vital implications for the fate of the offspring, and scientists have made great strides in understanding how genes control the fruit flies' choices from among an array of options (too much sugar in the medium and they turn up their little ovipositors, or egg-laying organs, at it). But the flies do not have to consult with their families about their decisions, and no one else offers an opinion.
The bees, however, live in a society, and while it is not democratic, neither is it a dictatorship. The queen may have the last word in reproduction, but not in moving house. Maurice Maeterlinck, the playwright who praised the nobility of ants and their cooperative nature in his 1930 book, had written The Life of the Bee in 1901. He considered the way the colony found its way to its new home, and concluded, "All things go to prove that it is not the queen, but the spirit of the hive, that decides on the swarm." As with house hunting in humans, the decision about where to move in honeybees and other social insects is fraught with complication. The decision must be made fairly quickly, because the swarm is vulnerable as it clings to a branch (or garage ceiling beam). At the same time, its consequences are crucial, since the colony will spend its life in its new home and needs to have ample room to raise its brood, with food sources located nearby. How do the bees keep from spending endless time in filibuster and argumentation, like a miniature all-night congressional attempt to arrive at a budget? What is more, sometimes the old home is destroyed by fire, flood, or the untimely arrival of a hungry bear, necessitating the abrupt evacuation of the old home and a pressing need to find a new one. A group decision is essential; the bees can't simply go back to their constituents and try again next season.
Group decisions are particularly interesting because they imply first that the members of the group are able to convey messages to each other, and second that they have some mechanism for evaluating each individual's contribution. Groups have a rather dubious reputation when it comes to collective activity; none other than Friedrich Nietzsche disparaged humans by suggesting, "Madness is the exception in individuals but the rule in groups." Maeterlinck, however, was more charmed by the process of group decisions in the bees and felt that "there can be no doubting that they understand each other," although "certain as it may seem that the bees communicate with each other, we know not whether this be done in human fashion." The bees exhibit what is called a consensus decision, which means that they choose between several mutually exclusive alternatives and then all abide by the selected one. This process is similar to what goes on in a democratic election, or in international treaties signed by a number of nations with a common goal. Everyone doesn't necessarily contribute to the decision, but they all agree to do the same thing in the end.
Consensus decisions are distinguished from what are called combined decisions because they require everyone to concur, which means the group has to possess a fairly sophisticated means for exchanging information. A combined decision is made when the individuals in a group simply assign themselves different tasks, for example, the allocation of hive cleaning versus foraging in bees, but don't all agree beforehand on a list of who will do what. The distinction is important because getting everyone to agree to a single outcome means that they may have to sacrifice their own interests in doing so, a rather advanced capacity for a tiny insect. Many scientists first started thinki
ng about the possibility of a "hive mind," that controversial greater-than-the-sum-of-its-parts superorganism, when pondering the way that social insects choose a new place to live.
Aristotle had noticed that it seemed as if bees received information from scouts that had made advance sallies to find potential nest sites, but the process of deciding on a new nest site was first studied in detail in the 1950s by a German zoologist, Martin Lindauer. He happened upon a swarm near the Zoological Institute at his university in Munich and noticed that a few of the bees on the outside of the swarm were performing the same waggle dance that his mentor, the Nobel laureate Karl von Frisch, had described in the context of signaling the whereabouts of food sources. Since the bees had no pollen or nectar, Lindauer wondered if they might be signaling not the location of a patch of flowers, but the possible place the swarm might settle.
By recording the different locations encoded in the dances of the apparent scouts, Lindauer noticed that although the bees seemed to be dancing "for" many different sites at first, eventually they seemed to settle on just one. Soon after this winnowing of alternatives, the swarm rose in a body and took off for the site that had made it to the finals. In the decades that followed Lindauer's work, scientists established the characteristics that bees would use in their description of a dream house to a bee real estate agent, including a south-facing entrance, a small enough entrance hole to discourage unwanted visitors, and enough room for an average-sized honeybee colony to spread out in comfort. The ability to compare several different possibilities, like enterprising couples scanning the online real estate ads, indicates a rather sophisticated cognitive ability on the part of the insects and has even led to the suggestion that the bees possess some form of consciousness. Why being able to choose a split-level ranch over a refurbished Victorian is peculiarly emblematic of higher intelligence, while other decisions are not, is unclear to me, but it is undoubtedly a complicated decision.
In the 1990s, Kirk and his former advisor, the eminent bee expert Tom Seeley at Cornell University, began to work with other colleagues to determine how the selection of just one site was made. One swarm took about 16 hours of dancing, spread over three days, to reach a decision, with eleven different potential sites taken under consideration before the winner was determined. In a New York Times column, James Gorman noted that the scientists were, like Maeterlinck, convinced that the bees arrived at decisions that were good for the group, and that "Dr. Seeley is a bit more cheery than Nietzsche," a comparison that was probably novel for both the entomologist and the philosopher.
So how do the bees choose the winner? The idea of a bee version of polling the hive constituents to get a sense of everyone's views on the various sites before arriving at an informed decision is appealing, but it turns out that this is not how the bees decide which scout to follow. Instead, they seem to be sensing a quorum of dancers "for" a particular site, and then the entire swarm follows the quorum.
Kirk, Seeley, and Kevin Passino of Ohio State University made this discovery using bee colonies on Appledore Island off the coast of Maine, where Cornell has a research facility. The island was handy because it has almost no trees that could serve as natural nests, which means the scientists could provide all the potential homes for the colonies they brought there.
The scientists gave different swarms of bees on opposite sides of the island either just one nest box into which they could relocate, or five similar boxes set close together. If the bees required a quorum of dancers, the dilemma of five equivalent alternatives should delay the formation of the quorum and, hence, delay the swarm movement itself, but the rest of the decision-making process would be the same in the two cases. As predicted, the bees took an average of 442 minutes to arrive at a decision when they were spoiled for choice, as it were, compared with just 196 minutes when one box was available. "Group intelligence," the researchers concluded, "is a product of disagreement and contest." Whether that constitutes more optimism than Nietzsche is perhaps a matter of debate.
Kirk and Tom Seeley also determined that the bees dance differently depending on the quality of the site they have discovered; scouts spent equal amounts of time inspecting two potential sites that were offered, but performed more circuits of their dance back at the swarm for the better location. The bees also avoid getting drawn into agonizing fruitlessly over a poor candidate by the rapid decrease in sequential visits to a lower-quality site, so that they are able to ruthlessly reject a loser instead of second-guessing themselves, something more humans would probably do well to emulate.
How the bees assess the presence of enough scouts to constitute a quorum is still not well understood. The swarm does not always arrive at a unanimous decision; occasionally one will split at takeoff, and even when dissention is not so drastic, a few divergent dancers will still be rooting for their own selection up until the very last minute. Until very recently, scientists likewise could not understand how the group of bees could all get up and move in synchrony after the winning site was selected. The scouts produce a kind of rallying cry, called piping, that seems to energize the swarm to warm up before they take off in unison.
Some work by Seeley and Clare Rittschof of the University of Florida suggests that the scout bees work the crowd by moving among the more languid members of the group, making a stereotyped set of motions accompanied by sounds, called a buzz-run. The buzz-run seems to encourage any laggards to move their wings as well, which in turn ensures that everyone's wing muscles are sufficiently warmed up for flight. Because they are cold-blooded like other insects, bees need to reach a certain temperature before they can fly, and they do so by revving their muscles like diminutive engines. Rittschof and Seeley then proposed that the scouts act like swarm thermometers to gauge the temperature of the mass of bees and trigger its synchronized takeoff when everyone is ready.
Even after takeoff, the synchronicity of the swarm is amazing. Although the scouts have done their advertisement and the decision has been made, less than 5 percent of the bees in the swarm have actually been to the site themselves and, hence, don't know exactly where to go. Yet all of the ten thousand or more end up in the right place, often miles away. Another publication with Seeley as the bee expert, this time with engineer Kevin Schultz from the Ohio State University as a collaborator, gave the solution to this problem as well. Using high-definition films of the swarms on Appledore Island, the researchers examined more than 3,500 frames of bee movement and determined that the informed few fly through the top half of the swarm at high speed to lead the way. These leaders are called streaker bees, after their cometlike movements in the cloud of insects.
Microscopic Real Estate
PEOPLE have long taken a personal interest in the real estate preferences of honeybees, mainly because the product of a smoothly running hive is relevant to human well-being. They have been less concerned about the decisions made by other social insects, such as ants, so long as they do not decide to relocate in or near human habitation. The house-hunting behavior of ants, however, is both similar to and different from nest site selection in honeybees, and the contrast is instructive.
Much of the research on group decisions by ants on where to live has centered on a couple of species with life histories that sound like they come from a fairy tale, or maybe a Winnie the Pooh story. The insects are even tinier than the ants commonly seen in kitchens, and use either rock crevices, or, more charmingly, acorns, as their place of residence. The entire colony, queen and all, can fit into a space smaller than a person's thumb. Needless to say, this makes replicating their world in the laboratory extremely easy; one of the foremost researchers on these ants, Nigel Franks of the University of Bristol, makes little homes for them by gluing a bit of cardboard between two glass microscope slides to recreate a crevice that is also easily spied upon.
The ants' house-hunting activities have attracted attention mainly because they use the tandem running procedure I described in the chapter on learning to help their nest mates find th
e new location. As in the bees, ants send out scouts to search for new homes, but unlike the bees, the scouts enlist enthusiasts for the new cavity by the same "follow me" motions used to direct other colony members to food sources. The ants don't perform waggle dances like the bees, but they will recruit for good sites more quickly than for poorer ones. The new recruits, if they concur with the desirability of the chosen location, then get others to join them. If you are an ant living in a small dark hollow, the best home has a narrow entrance with dim light, presumably to discourage predators, and just the right amount of floor space. The ants can even evaluate the potential for nasty neighbors, in the form of a foreign ant colony, and eschew such potentially troublesome locations.
At this point the process diverges from that of the bees, because once a site is selected by enough ants, the process becomes one of shanghai rather than persuasion, as the remainder of the colony is simply picked up bodily and carried, head ignominiously pointing backward, to the chosen location. Carrying is three times faster than tandem running, and once the carrying starts, the ants are committed to their new location and do not switch preferences in midstream. Regret, it would seem, is not part of the ant repertoire. As a paper by Robert Planqué and his collaborators, including Franks, puts it, "Ant colonies have found a good compromise between impatience and procrastination." Would that we were all so prudent, at least when it comes to moving house.
In human groups it's often the case that the larger the crowd, the harder it is to reach a decision, whether about going to war or choosing a restaurant. In contrast, the ants seem equally good at determining the best nest site from among an array of options presented in the laboratory regardless of the size of their colony. The larger colonies do use more of the tandem runs to exhort others to follow them, and seem to need a larger quorum of assenting individuals before they decamp. Interestingly, both small and large colonies select sites that will comfortably contain a colony that has grown to full size, suggesting that the ants can anticipate their future needs, a remarkable feat.