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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,