Sex on Six Legs: Lessons on Life, Love, and Language from the Insect World - Marlene Zuk (2011)
Chapter 3. The Inner Lives of Wasps
Personality in Insects
IN The Sword in the Stone, T. H. White describes how the magician Merlin educates young King Arthur by turning the boy into various beasts: a fish, a snake, a badger. He transforms young Wart, as he is called, into an insect only once, and that only because Wart is confined to his bedroom, with Merlin shouting at him through the door, and more substantial spells have a hard time entering the keyhole. (The logic of this constraint has puzzled me ever since I first read the story as a child, given Merlin's other superior abilities, but perhaps White felt it necessary to find some justification for why one would ever become an insect in the first place.) In any event, Wart becomes an ant, and it is not a happy transformation. Instead of being thrilled at, say, his ability to lift objects heavier than he is, or his exquisite sense of smell, or his remarkable ability to walk on vertical surfaces, the ant-boy is horrified by the lack of individuality among his nest mates. Each ant (with its "mute, menacing helmet of a face") is like every other, obeying the rules of the queen without questions, and a sign above the tunnel states, "Everything not forbidden is compulsory," a slogan that Wart "read with dislike, though he did not understand its meaning."
Although the ants turn out to have many unpleasant qualities, the most chilling one is that they are automatons, with no independent thoughts, designated only by numbers and letters and interchangeable in their repetitive tasks of collecting food and burying their dead. This image of insects, particularly the social species such as ants and bees, is behind countless dystopian views of the behavior of extraterrestrials in science fiction, perhaps best personified, if that is the correct term, by the Borg of Star Trek. These cyborgs assimilate all other beings that cross their path, intoning, "Resistance is futile." They have a queen, work unceasingly, and most crucially, like the ants in White's book, lack all individual identity, having sacrificed it for the good of the group.
Nothing is more important to us than our uniqueness as individuals, and we point to our different personalities as evidence of our humanity. Conformity within the tribe may be valued differently across cultures, but no one thinks a society in which personality is subsumed by service to the state is desirable, even the most diehard communist. Individuality is something of an excuse for selfishness. And while we may freely admit to our pets being distinct individuals, or be willing to believe that a particular elephant or gorilla might be brave or shy, confident or anxious, the buck stops firmly at the backbone. Invertebrates in general, and insects in particular, are assumed to be milling masses of sameness. Perhaps the idea of them as automatons is part of what we find so terrifying about swarms of locusts or bees: each individual is seen as interchangeable with every other, so that killing one has no effect on the rest of the group. They just press on, relentless zombies in our fields and kitchens.
And yet, as with so many other stereotypes about insects, this one turns out to be wrong. They do have personalities, or versions of them, which leads us to question not only the function of individual differences in animals, but in ourselves. We may take pride in individuality, but what is it for? And if being individuals doesn't set us humans apart, what does?
Waspishness in Wasps and Boldness in Spiders
ALTHOUGH psychologists can argue endlessly over definitions of personality, most of those definitions contain some version of individuals showing consistent differences in how they feel and behave. Someone who is aggressive today will be aggressive tomorrow, and aggression in the boardroom means aggression on the basketball court. We also talk about temperament, the predilections that seem to be present when we are born and that shape the formation of personality later on; a fussy infant may become an anxious adult. Sam Gosling, a psychologist at the University of Texas who studies personality in animals, notes, "In some cases, the word temperament appears to be used purely to avoid using the word personality, which some animal researchers associate with anthropomorphism."
It is true that having a personality seems to imply that one has emotions, a slippery slope when referring to animals, although many early researchers, including Charles Darwin, had no trouble with making the leap. Darwin wrote an entire book on the topic, titled The Expression of Emotion in Man and Animals, and while he concentrated mainly on mammals and whether, for example, baring the teeth in dogs had its counterpart in human sneers, he did not exclude insects: "Many insects stridulate by rubbing together specially modified parts of their hard integuments. This stridulation generally serves as a sexual charm or call; but it is likewise used to express different emotions. Every one who has attended to bees knows that their humming changes when they are angry; and this serves as a warning that there is danger of being stung."
Far be it from me to contradict the founder of evolutionary biology, but I don't see it this way. Just because a beekeeper—or Darwin—can predict that a bee is going to sting doesn't mean said bee is flooded with rage. It just means that the beekeeper is skilled at reading the bee's signals, like a weather forecaster knowing when a storm is coming because of the quality of the wind and clouds. Animist beliefs and poetic license aside, we don't conclude that the storm is angry either.
Like most modern biologists, I think insects have personality but think it is presumptuous, not to mention anthropomorphic, to claim that they have humanlike feelings. It is simply too hard to know what is going on inside another being's mind, even when that being is another human, and it seems safe to say that whatever an ant is feeling, it probably isn't the exact same thing humans feel. We are particularly hampered by the lack of facial mobility in many animals, including insects, which makes them even harder to identify with. It's hard to look into the eyes of a butterfly and feel a connection with the being within. Reading expressions is key to our assessment of mood and, hence, personal characteristics, so the absence of frowns and narrowing eyelids in many species (not to mention the eyelids themselves) means that we must use other cues in assessing animal personality.
But as I do with so many other aspects of insect life, I find the absence of humanlike emotions both challenging and soothing. Challenging because if insects lack feelings, where do their personalities come from? Insects make us ask more and more exacting questions about them, keeping us from sloppy generalizing that assumes they are just like us. And soothing because the insects exist, complete and lovely, in their own world that works just fine without the rules and assumptions that govern human behavior. We think—we know—we would be horrific shadows of ourselves without emotions, and we assume that our personalities stem from the way we feel. But if insects can have personalities without emotions, we have to look harder for the source of those characteristic differences among individuals. Maybe personalities are just collections of traits, like body shape; one is viewed as heavyset or sylphlike because of the shape of one's limbs, the size of the joints, length of the fingers all working together to give an impression of bulk or slenderness. The personality has different components than the body, but it is all still the same thing, and insects show us a reduction down to essentials once again.
Not all scientists have been willing to accept that insects lack emotions. Donald Griffin, who discovered the details of echolocation in bats and studied animal communication for much of the last half of the twentieth century, spent the later years of his life trying to convince his fellow scientists that nonhumans—whether dolphins, chimps, or honeybees—can possess what he unabashedly called consciousness. He challenged the prevailing view that consciousness, and by extension true emotion, is so subjective that one can never know if others share it. Instead, he defined consciousness pragmatically, as the "versatile adaptability of behavior to changing circumstances and challenges." By that token, insects certainly qualify, and Griffin was fascinated by the complex communication of social insects such as ants and bees. He dismissed concerns that the small brains and differently organized nervous systems of insects precluded consciousness as immaterial, asking, "What underlies this dogma that only a vertebrate central nervous system is capable of organizing thoughts?...The behavior of some insects is far more flexible and versatile than previously recognized. Perhaps this new behavioral evidence will modify our long-standing conviction that all invertebrates are thoughtless automata."
I like the idea that we have been underestimating insects, but I think we are on very shaky ground extrapolating our own feelings to beings so different from us. Calling insects conscious, or saying that their variable personalities mean they are much like people runs the risk of not paying attention to what they are actually doing, and instead assuming that they are little people in chitin suits. In the long run, I find it more rewarding to see them as insects, and leave the question of their awareness alone.
Scientists therefore simply rely on the outward behavior of an animal, often under controlled experimental circumstances, to tell them something about its personality. If you place a mouse in the middle of a bare room, is it likely to explore, or huddle in a corner? Does another mouse do the same thing? And if one animal is an exploratory type, does that mean it is also likely to be exceptionally aggressive toward other members of its species? It turns out that it does. The "bold-shy continuum," with some individuals eager to explore and others more risk averse, has been documented in several kinds of animals as well as humans, with evolutionary biologist David Sloan Wilson providing some of the landmark research on the topic. He points out that it is important to remember that being shy, whether in people or sunfish, his favorite study system, is not equivalent to being a loser; in other words, there is something more going on here than just dominance over food or nest sites. Instead, animals take their place on the continuum independent of other determinants of dominance, for example, how large they are and, hence, how likely to win a fight.
Over the last few years, biologists have also noticed that some individual animals, whether they are fish, ferrets, or fruit flies, tend to show predictable suites of traits, not merely characteristics such as boldness or shyness during a single event. The predictability can happen in two ways. First, an individual that is, say, bold when faced with a predator will also be likely to be aggressive and attack another member of its species, so that its behavior under one set of circumstances predicts a different kind of behavior under another. Second, an animal that is bold today will be bold tomorrow, and one that hangs back will hang back all the time. In another effort to avoid anthropomorphism, or perhaps just because of a fondness for jargon, scientists often refer to these repeatable clusters of traits as behavioral syndromes, a phrase that evokes a bit of the pathological to me—are there behavioral syndrome support groups? Regardless, biologists do use the terms boldness and shyness to refer to animals, particularly fish, for some reason, and bold sunfish are those that are more likely to inspect a predator introduced into their tank, as well as acclimate more quickly to being in the lab and forage more voraciously. These behavioral characteristics can have long-ranging consequences; the bold and shy fish even differ in the parasites they harbor, probably because the different activity levels mean that each type hangs out in a slightly different environment and is exposed to different diseases.
Be that as it may, scientists don't try to replicate the five commonly used axes for personality in humans: extraversion/introversion, antagonism/agreeableness, conscientiousness, neuroticism, and openness to experience. Too many of those criteria require self-reporting, but equivalents can often be measured, for example, the frequency of fighting that occurs when animals are in a group, or the length of time it takes an animal to move through its enclosure. Gosling cautions that it is important to know the standards against which the measures are being compared; after all, he points out, if one asked whether a deadly black mamba in a room was aggressive, it would be possible to respond that it was not, if "it has attacked only two people in the last hour, well below the norm for this species of snake." Nevertheless, one would still be ill-advised to enter. There is also something called The Horse Personality Questionnaire, with categories of Dominance, Anxiousness, Excitability, Protection, Sociability, and Inquisitiveness; why horses require six descriptors while humans only need five is an interesting question.
Keeping this in mind, a wide range of animals, including several insects and spiders, show consistency in their behavior. For example, fishing spiders live at the edge of ponds and feed on insects near the water. Different individuals attack their prey with differing degrees of alacrity, and the individuals that leap upon their prey more quickly get more food. This seems like an all-around good thing, until you learn that predatory eagerness in females is also associated with a greater likelihood of killing and eating one's potential mate. Fishing spiders also respond to the threat of attack by a potential predator by quickly diving under the water and remaining submerged in an air bubble until the danger is perceived to have passed, a period that can exceed 90 minutes. J. Chadwick Johnson and Andy Sih at the University of California, Davis, found that the length of time female spiders spent submerged varied among individuals, and bold spiders—ones that emerged relatively quickly from their underwater shelter—were also likely to go after food more decisively and to respond to males that were courting them by tapping the water surface.
Because I study them, I am biased toward crickets and have always thought they had plenty of personality, with more of it, not to mention charm, than their relatives the grasshoppers. Male crickets are rather pugnacious, and the ancient Chinese often pitted them against each other in specially constructed arenas, much like miniature cockfights. Some individuals were highly prized as winners, with poems written about their prowess. And indeed, my intuition was upheld; recently, Raine Kortet and Ann Hedrick found that fighting ability in a North American cricket was not only variable among different males, but winners were more brazen about emerging from a refuge in their container after they had been disturbed in a manner simulating a predator.
Water striders are the leggy insects that dimple the water of streams and ponds all over North America; they skate over the surface, grabbing both prey and, during mating season, each other. More accurately, male water striders jump on females and attempt to mate, while the females often try to shake them off. Although they all look similarly jittery to the casual observer, the striders, too, vary among themselves in their level of activity, with relatively sluggish individuals and more perky ones. More active individuals also tend to be more aggressive. Andy Sih, working with Jason Watters this time, created groups of male water striders in semi-natural streams by putting like-minded, or at least like-behaving, individuals together, so that some groups had members that were more laid-back overall, and others those that were more likely to hustle. The scientists then put females into the mix and measured the success of the males in obtaining mates. Somewhat to their surprise, the groups that measured the highest on the hard-driving scale didn't end up with the most overall mates. Watters and Sih discovered that such groups were likely to have "hyperaggressive" individuals whose overenthusiastic pursuit apparently drove the females away. As with humans, it's easy to overdo the hard sell.
Even those poster insects for uniformity, tent caterpillars, turn out to have some inner uniqueness. Tent caterpillars live in rather messy webs spun in tree branches and can number in the thousands during outbreaks, when they are serious forest pests. Their munching, marching armies can defoliate tens of thousands of acres. Understanding variations in their behavior is important for controlling them, so the topic has received considerable study, and it turns out that individual caterpillars show consistent distinctive patterns of sluggishness or activity over several days. Admittedly, how much a caterpillar walks or eats during an hour-long observation period, and whether it is more or less than the amount attributable to another caterpillar, is not what most people think of when they imagine an animal with a characteristic personality, but it still differs from that Borg-like image that is traditionally held.
As for Wart's—and T. H. White's—stereotypes about ants, they too may not be well founded. In his delightfully titled 1928 paper Psychological Experiments with Ants, G. Kolozsvary studied the escape behavior of the insects and found that they varied in what he termed nervousness. Other more recent papers have found individual differences in how ants cared for the pupae in the nest and how they responded to the others in the colony.
So personality is everywhere, even if Arthur, the once and future king, remained unconvinced. One of the most interesting implications of this realization is that scientists are starting to have what might be termed a more holistic view of animal behavior. If how an individual behaves now can be predicted based on the way it behaved before, we should probably stop acting as if every day, and every experiment, is a world made new—looking at an ant or fish or cricket under one set of experimental circumstances isn't independent of looking at that same animal under another set. This means that even biologists should see the animals they study as unique individuals at least sometimes, rather than interchangeable subjects. We've shied away from this before lest we appear anthropomorphic, but now it seems as though there are solid scientific reasons not to assume that all ants are the same.
She Must Get That from Your Side of the Family
WHERE do personalities come from? In other words, are we—and other animals—born with them, or are they shaped by our experiences? It's particularly instructive to ask these questions about insects, because with humans and other cognitively complex vertebrates, it's virtually impossible to disentangle the two. We humans are interacting with others nearly nonstop from the moment we are born, and maybe even before that if the exhortations about talking, reading, or playing music to the developing fetus are to be believed. Other social animals such as dogs or primates are almost the same. But insects have a much more modest amount of input from others, and as I have said repeatedly, we can manipulate their environments much more easily as well. Therefore, any behavior that persists despite a change in juvenile milieu must be genetic, and conversely, a behavior that is different in genetically similar individuals, for example, siblings, that are reared apart is likely to be due to learning.
Like many traits, shyness and boldness seem to be at least partly heritable; if an individual's father or mother was bold, chances are that it will be too, even if it is reared apart from its parents. Using fruit flies, Marla Sokolowski has been able to find not only a single gene, but its coded protein that lies behind a tendency to either move around as a larval fly (rovers) or have a more couch potato-like persona (called, reasonably enough, a sitter).Humans have also been able to domesticate breeds of horses, dogs, and other animals that possess not only particular body types but also characteristic behavioral traits, including willingness to fetch (retrievers) and aggressiveness (think pit bull), which means that such characteristics must be able to be passed from parents to offspring. Bold and shy people have different responses in their brains when they are presented with the same photographs of familiar or unfamiliar people, suggesting that these differences are an integral part of our makeup.
But as is also the case for many traits, the environment affects how much boldness or shyness (or any other aspect of personality) is expressed. Early experiences such as how much a mother interacts with her offspring can modify the tendency for an animal or person to be reckless or reserved, docile or rebellious. For many insects that lack any parental care, later behavior can still be affected by the place where a mother lays her eggs. In Wilson's sunfish, boldness means that you explore a new object in your pond sooner than the other fish do, and you are more willing to come out of hiding when a predator approaches. These differences between bold and shy individuals persisted in the wild for as long as Wilson and his crew were willing to look for them. And immediately after they were brought into aquaria in the lab, the bold fish were more willing to eat fish flakes, a novel food, instead of sulking in a corner, dreaming of scrumptious snails. But after a few weeks of getting used to the glass and plastic of their new digs, the distinction between the two types disappeared, and the formerly bold and shy sunfish were equally likely to approach a new object. The real world, it seems, keeps us—or at least some animals—different. These results make it tempting to speculate about the homogenizing effects of institutions such as prisons, or maybe even just urban living, on us humans; but of course we don't have a similar controlled experiment on people to use for comparison.
This universality of personalities across many different kinds of animals, including insects with their tiny brains, has two crucial implications. First, it means that the mechanism behind personalities can't be all that important, or at least that different parts of our physiology must account for the existence of personalities in different groups. In people and other mammals, we attribute, maybe even excuse, being laid-back or anxious to our hormones. Our stress levels are up because of cortisol or adrenaline, our neighbor is phlegmatic because his testosterone has decreased as he's aged. It isn't that hormones cause us to have particular traits, but that we have to have some physiological manifestation of our psychic differences. Even things that seem to be all in our head have to come from somewhere in the body, whether that is hormones coursing in the blood or electrical signals leaping in the brain.
Invertebrates, however, lack the same kind of hormonal system that mammals have, so their tendency to dart across a pond or cower under a leaf must arise from a different physiological source. The hormones are a handy means to an end, but they are not the only one. If fish, ants, and crickets have personalities too, we have to look somewhere other than our vertebrate types of tissues and organs for where they come from.
Second, when something seems to have evolved independently over and over again, such as wings in bats, birds, and butterflies, you have to suspect that nature is onto a good thing. So the existence of something that looks so much like our personalities, but is obviously evolutionarily independent, suggests that having a personality serves an important function.
The Face Is Familiar, but the Sting Is Different
IMPLICIT in the existence of different personality types is the ability to tell each other apart. If you can't keep track of whom you're dealing with, knowing that someone is rude and someone else magnanimous is useless. Young Wart was taken aback by the sameness of the ants he encountered, each distinguishable only by a set of letters and numbers (the Borg, too, were designated by numbers, with the voluptuous Seven of Nine, taken into the Voyager starship community, using her lack of a humanoid name as an indication of her loss of humanity). The implication was that since all the individuals behaved the same, there was no point in distinguishing among them, either by appearance or appellation. And yet if animals have personalities, and others react to them as individuals, they must not be indistinguishable. We can tell our pets apart, and we are perfectly happy to watch nature shows that differentiate—and name—individual elephants or meerkats. But what about insects?
One roach or ant may look just like the next to us, but when Liz Tibbetts of the University of Michigan puts up a slide of the paper wasps she studies, she calls the array of face shots portraits, and she does it unselfconsciously. To her, they are just as distinctive as a series of family holiday photos, or a row of oil paintings of ancestors on the manor wall. And indeed, once you scrutinize the lineup, the yellow triangular faces do differ: a couple of black dots across the forehead of one, a big dark triangle across the chin of another. For over a century, conventional entomological wisdom held that given the large numbers of individuals in a social insect colony, the most one could hope for in terms of individual recognition would be a rough ability to classify other wasps (or bees, or ants) into categories: male versus female, or nest mate, to be fed or at least tolerated, versus foreigner, to be attacked. Maybe it is the opposite of anthropomorphism: instead of assuming animals are like us, we assume they are not. Both are risky generalizations that turn out not to be borne out by the facts. Increasingly, biologists such as Tibbetts are discovering that at least some insects can do far more than peer nearsightedly at their neighbor and call it friend or foe.
Paper wasps, unlike honeybees, live in relatively small groups of females, all of which are capable of laying eggs, so they lack the clear distinction between worker and queen. The females of one of the species Tibbetts studies, Polistes fuscatus, fight vigorously for dominance at the beginning of the season. The rank an individual attains is crucial, because the higher up a wasp is in the hierarchy, the more food she can garner, the less work she does, and, most important, the more eggs she contributes to the colony's reproduction, giving her a larger share of genes in the next generation. But Tibbetts noticed that, as with other species that live in socially stratified groups, for example, baboons, the overall amount of aggression in a wasp nest subsides with time, and the wasps do not have to fight each time they meet to reestablish who's boss.
Tibbetts suspected that the wasps used their variable facial patterns to recognize and remember individuals, and she tested her idea in an ingenious if simple way: she painted the faces of wasps so that they no longer seemed familiar to their nest mates. To minimize her risk of getting stung, she nabbed the wasps early in the morning, when the wasps were chilly and less inclined to object to being handled. Once the redecorated insects were returned to their nests, Tibbetts watched the reaction of the rest of the colony. As she had predicted, the wasps were much more aggressive to the altered individuals than they had been before, although the aggression subsided after about half an hour, indicating that they had learned the new facial pattern of their nest mate. It was clear that the wasps were not simply reclassifying the painted females into rough categories, such as "familiar" or "unfamiliar," because paper wasps use chemicals on their outer surface for that purpose; furthermore, a female perceived to be from outside the colony would have been ripped to shreds or chased away, not simply pushed around a bit more than before. What is more, the wasps didn't seem to care how the apparent interlopers were painted—a bit more yellow on the chin garnered no more or fewer attacks than a larger brown stripe between the eyes. That means that the wasps are not using the face patterns as an indicator of size or age or some other quality of an individual, but instead as genuine identity tags; having two black spots, for example, doesn't say, "Stay away from me, I am large and fierce," but rather, "Sam I am" (or Samantha, in this case).
In another species of paper wasp, P. dominulus, facial patterns do indicate both size and dominance, and females pay particular attention to the blotchiness of the black marks. A more broken pattern means a robust, higher-quality individual, for reasons that aren't yet clear. This time, Tibbetts painted the faces of the females so as to either make them look more or less dominant, and then allowed the wasps to guard a sugar cube in the lab; in the wild, the wasps eat nectar, but they happily consume sugar in captivity. Pairs of wasps, one painted to look like a subordinate and one to look like a dominant individual, were each assigned their own sugar cube, and then another wasp was introduced to the container. The wasps share food, but dominant individuals are harder to coax into contributing than submissive ones. As you might expect, the supplicating wasp was more likely to choose a cube being defended by a wasp whose facial pattern suggested she was a loser. What's more, when Tibbetts staged encounters between wasps that were strangers to each other, a subordinate individual painted to look like a dominant one was much more likely to be beaten up by the real dominant wasp, showing that even wasps dislike a cheater. Interestingly, other researchers studying the same species of wasp found that body size, rather than pattern, was important in determining social rank in a population from Italy (Tibbetts works in North America); the reasons for the difference are not well understood but may have something to do with the timing of food shortages and, hence, growth of the young insects.
It turns out that individual recognition is more likely to evolve in wasp species that show more complex social behavior than in those with more short-lived or simple interactions. In some species of paper wasps, a single female always starts a nest, and her daughters then contribute to the growth of the colony. In others, several females build the cells and attempt to lay their eggs simultaneously, giving rise to the jockeying for social status described above. Among yet a third group, either approach is seen. Each of these scenarios calls for an increasingly astute approach to social politics. As one might expect, species that are likely to have complicated group dynamics, as indicated by the likelihood that multiple individuals will have to work out their hierarchy, are more likely to show a lot of variability in their markings.
What about Wart's ants? Contrary to his experiences, they too can recognize individuals, although unlike the wasps, they lack the distinctive facial or other body patterns used to tell one six-legged companion from another. Instead, ants use chemical signatures, individual odors that ants produce on their external skeletons. We have known for a long time that ants as well as many other insects use such chemicals as general news bulletins—"I am one of you; let me through," or "Female here, sexually available till six"—but had always assumed that such rough categories of signals were the limit of their abilities. But Patrizia D'Ettorre from the University of Copenhagen in Denmark and her colleagues wondered whether ant queens in one species, at least, might do something similar to what the paper wasps do.
Most ant colonies have a single queen, who settles into a life of fecund bliss after a single mating flight in which she left her home nest, mated, and then spurned any further gallivanting by chewing her own wings off and digging a chamber for her eggs underground. But in a tropical ant species called Pachycondyla villosa, which lives in forests from southern Texas to Argentina, several of the young queens (older literature actually refers to them as princesses, though this terminology is not seen much any more) band together to make a nest in a bit of rotting wood and form a society with a dominance hierarchy and division of labor among the members. As with the wasps, it stands to reason that sorting out whose turn it is to take out the trash would be easier if the ants could tell each other apart. D'Ettorre tested this idea by collecting some of these new queens in Brazil and allowing pairs of them to establish a dominance relationship in the lab. The ants fight by biting, stinging, and boxing with their antennae until one party backs off. Then each queen was allowed to interact with either her former companion or an unfamiliar female. In some trials, D'Ettorre anesthetized the ant her subjects were given to ensure that it was really an individual odor cue, and not just generally aggressive or submissive behavior, that could be used to distinguish one ant from another. In all cases, both the dominant and subordinate queens recognized their former partners. Chemical analysis of the ants' exoskeletons showed no relationship between any particular compound and whether a queen was dominant or subordinate, confirming that the ants were not simply reacting to a generalized "alpha ant" smell. What was even more astonishing was the ants' memory: even after 24 hours of separation, a hefty interval for an animal that lives just a few weeks or months, the queens remembered their previous encounters and behaved accordingly when the two females met (whether there was any frantic internal searching for identity, a kind of ant version of "You smell so familiar but I just can't remember who won when we were together," wasn't discussed).
Finally, what does being able to distinguish a tiny blob of black or yellow, and remember who has which variant, mean about the brain of the insects that exhibit such a sophisticated ability? In many animals, the part of the brain controlling a much-used behavior is comparatively larger than in species that seem to need it less; thus, for example, bats and owls have disproportionately large portions of their brain devoted to hearing. Neurobiologists Wulfia Gronenberg and Lesley Ash checked out Tibbetts's wasps, as well as other closely related species, and found that being able to recognize faces didn't mean having a larger brain or larger visual centers. Interestingly, the wasps with the recognition abilities had smaller olfactory centers. Another part of the brain with the rather peculiar name of mushroom body was larger than expected, but the difference was quantitative rather than qualitative, suggesting that such a capability is nothing that unusual among wasps, and that similar abilities may be discovered if we simply look for them.
Personalities and Evolution
ALTHOUGH individual variation in animal personalities is a somewhat novel idea for biologists, variation itself is not, being the stuff that underlies evolution. Natural selection acts by some variants reproducing better than others, leading to a preponderance of the fitter genes in the population. But this seems like a paradox in the consideration of personality as consistent differences in 't some of them perform better than others? And if so, why haven't the more successful ones come to outnumber the less successful ones, so that we are left with only those personality types that are optimal for their environment?
This question is part of a much larger one, namely, what maintains all the tremendous variability that we see in nature. It's all very well and good to natter on about snowflakes, but living things are far more distinctive. Mutations, changes in DNA that occur spontaneously or as a result of environmental forces such as radiation, supply the raw material for evolution to act upon, of course. But mutations are just the original source of variation; differences among individuals persist in populations over many generations.
Scientists have a number of theories about how genetic variation is maintained in populations, ranging from the simple notion that selection may not have had a chance to weed out loser genes in some cases, to elaborate ideas about interactions among the genes that happen to be linked together on the same chromosome. Many of these explanations apply to the maintenance of different personalities, too, particularly the idea that advantages and disadvantages trade off against each other. Take the spider femme fatales, for example. Being exceptionally eager to snag a passing fly means that you are more likely to survive another day, which is obviously favored by natural selection: you get moved up a notch on the "likely to live long enough to have babies" scale. But being too rapacious in your treatment of a potential mate might mean lower likelihood of getting enough sperm to fertilize your eggs, which tips the balance in the other direction. On the other hand, a more suave approach to mates may be irretrievably associated with a more lackadaisical feeding style. Each personality type has its pluses and minuses under different circumstances, and they can all coexist because they each make trade-offs in different ways.
Of course, having a particular set of personality characteristics doesn't necessarily mean giving something up. Some individuals are just all-around winners, and if a behavior is advantageous all the time, then the individual exhibiting it makes out like a bandit and never pays the price. Being particularly active, for example, might mean that an animal finds more food, is more likely to be chosen as a mate, and is first in line for shelter when a storm threatens. Although our Puritanical sides may argue that everything has its price, sometimes that price is negligible. In cases where a trade-off within an individual doesn't exist, one might expect that selection would favor those lucky few, and variation might indeed decrease in the population.
Alternatively, having a particular personality type may be advantageous if your environment is not very predictable. Andy Sihlikens it to investing in the stock market; if you don't have any information on what is going to happen, it may be better to keep your money where it is than try to play the market, a particularly prescient point in today's economy. For an animal, being predator-wary all the time can be a good strategy when the actual likelihood of being eaten is unknown, a kind of better-nervous-than-sorry attitude. If on the other hand one can be reasonably sure that predators aren't lurking, then one can let oneself go a bit more, as it were, and act one way under some circumstances, and another way under others.
Yet another way that behavioral variation can be maintained is by having the success of some types depend on how common other types are in a population. If a group of, say, water striders is mainly composed of lethargic, cautious individuals, then being a fast-moving brave strider will be advantageous as long as the reckless types are rare, because the rare ones can dart in and grab food while everyone else is just gathering their thoughts. Once the fast movers reproduce and rise in abundance, however, the slower bugs can in turn do well, perhaps because their type is less likely to be nabbed by a predatory spider. Then the slow individuals do better, and so on; both types can persist over time, even if their relative numbers fluctuate.
Similarly, several researchers, most notably Judy Stamps at the University of California at Davis, suggest that personality trade-offs can have repercussions for how fast an animal grows and how many offspring it has. If you live hard and die young, but grow quickly and have your children early, you may end up leaving as many genes in the next generation as someone who grows more slowly, dies at an older age, and paced his or her reproduction more prudently over time. In other words, you could have a personality and life history more like a rabbit or one more like an elephant, and still be a member of the same species—an individual with characteristics at one of the opposite ends of the spectrum. Again, both styles can be maintained via evolution. The question is whether having an aggressive or bold personality is linked with a tendency to die sooner or have more offspring, something that bears investigation.
Another implication of personalities for evolution is that they make behavior less flexible. In an article summarizing recent work on animal personalities, Alison Bell from the University of Illinois said, "Animals do not always change their behavior as much as they should." While that "should" seems a wee bit judgmental to me (who are we scientists to decree endless flexibility among our animal subjects?), remember Ralph Waldo Emerson's admonition that "a foolish consistency is the hobgoblin of little minds." It is nice to think that insects and we have an equal opportunity to show small-mindedness, but what is the cause of this limitation? Bell speculates that it might just be too hard to change one's personality under different circumstances, even if it would theoretically be advantageous to do so; shifting around the hormones and nervous system reactions might require too much retooling of basic physiology. If the same evolutionary costs and benefits apply to human personalities, we may be better able to understand why some apparently counterproductive ways of coping in humans persist, and ultimately, why we have personalities at all.
Can We Have "A Feeling for the Organism" if the Organism Lacks Them?
IN EVELYN Fox Keller's 1983 biography of Nobel Prize winner Barbara McClintock, some of the geneticist's success is attributed to her "feeling for the organism," a way of understanding her scientific subjects that transcended traditional scientific data collection. Keller describes how the scientist had to immerse herself in the minute details of her study subject, understand "how it grows, understand its parts, understand when something is going wrong with it." The book, titled A Feeling for the Organism, became something of a symbol of science needing something more than facts and charts, requiring in addition an emotional investment from the investigator that verges on the mystical.
This all sounds fine and inspirational, until you discover that the subjects of McClintock's fascination are corn plants. Dotty gardeners cooing to their tomatoes aside, identification with anything other than pets and perhaps a few other animals such as wolves or ravens seems like so much New Age claptrap. But according to Keller, McClintock felt that people had a "tendency to underestimate the flexibility of living organisms." If that underestimation is true for corn, it is doubly so for insects. The idea that they are all alike, with identical reactions and identical lives, used to be unquestioned, as T. H. White illustrated. Now, though, we know better. The famous entomologist Vincent Dethier, author of the masterful book To Know a Fly and discoverer of many important aspects of insect neurobiology, fretted about the likelihood that his subjects had internal lives. In a 1964 essay about the continuum between insect and vertebrate brains, he said, "Perhaps these insects are little machines in a deep sleep, but looking at their rigidly armored bodies, their staring eyes, and their mute performances, one cannot help at times wondering if there is anyone inside." Nearly half a century later, and with the appropriate caveats about personality sans expression, the answer seems to be yes.