Insects are more numerous than any other animal, making up over 80% of all species. Estimates of the number of kinds of insects vary wildly, because new ones are being discovered all the time, but there are at least a million, possibly as many as ten million, which means that you could have an “Insect of the Month” calendar and not need to re-use a species for well over 80,000 years. Take that, pandas and kittens! At any one moment, say while you are reading this sentence, approximately 10 quintillion (10,000,000,000,000,000,000) individual insects surround you in the world.
Off-putting behaviors like consuming your mate after sex aside, insects seem to do much of what people do: they meet, mate, fight and part, and they do so with what looks like love or animosity. Ants tend aphids and scale insects as if they were tiny cattle. Bees convey the location of food using symbols. Unlike any other non-human animal, some insects live in sophisticated hierarchical societies, with specialized tasks assigned to different individuals and an ability to make collective decisions that favor the common good. They mirror most of our familiar behaviors.And yet they do all those things in stunningly different ways from humans, getting to what look like the same destinations without any of the same highway systems or modes of transport. That reflection we recognize is eerily superficial, because what drives the behaviors is not what drives our own. Underneath the maternal care, the language, the elaborate system of social favors given and returned, is a handful of nerve cells casually strung together in a few small clusters along the body wall. No cerebrum, no right and left hemispheres, not even that so-called “reptilian” brain part, the cerebellum.
Instead of a mirror, sometimes insects hold up a window, so that we can see through it and imagine what life with different ground rules. Insects wear their skeletons on the outside, and they insouciantly transform from egg to grub to gleaming adult in the space of days. Insects use their antennae to smell and hear in ways we cannot even begin to comprehend, with male moths detecting the odor of a receptive female from a single molecule released miles away. Some bees and butterflies can see in the ultraviolet range, giving them an array of colors we don’t have names for.All of that difference means that we can learn from insects without having to claim kinship so insistently, the way we do with the feathered and furred. To me that lack of identification with insects is precisely why we can look to them to gain insight into our own lives — we simply cannot anthropomorphize them into cute caricatures of humans.
We also keep coming back to insects because they are, however we may feel about them, extraordinarily important to the earth’s functioning as well as our own. Insects help aerate the soil by burrowing through it, and nourish it by leaving their droppings. They eat dead plants and animals that otherwise would clutter up the planet, and release the nutrients back to the soil. They control populations of other invertebrates and vertebrates alike, by eating them or their food or by making them sick. In turn, insects provide food for other organisms.
John Losey from Cornell University and Mace Vaughan of the Xerces Society for Invertebrate Conservation calculated the economic value of four crucial tasks performed by insects: pollination, recreation, dung burial, and pest control of animals that eat crops, including other insects. The total bill? Over $57 billion in the United States alone, and that just includes so-called “wild” insects, not domesticated honeybees or silkworms or other species that are reared commercially by people.
Insects are the great equalizers. There is not a corner of the globe where people — rich, poor, old or young — have not had some encounter with insects, even if only to swat a mosquito or crush a cockroach. Because of that ubiquity, insects are the easiest portal to the animal kingdom, an inadvertent and often unwilling reminder that other creatures live here besides us, whether we want them to or not. Insects also provide a much more uplifting egalitarianism. If you want to learn about the natural world, but are too young or too poor or otherwise lack an opportunity to study the stars or put droplets of pond scum under a microscope, bugs are always there for you. I grew up in the middle of Los Angeles in a modest neighborhood without creeks or woods or much in the way of encouragement to do a project for the science fair. But I reared the fritillary butterflies that lived on a passion flower vine in our yard, year after year, never tiring of watching as the eggs hatched into threadlike caterpillars that grew and grew inside my jars, eventually hanging upside down from a stick and becoming a gaudy spangled adult. No special equipment necessary, no need to venture anywhere my mother would disapprove of or that cost any money at all. And the results were just as compelling, maybe more so, than if I’d had a telescope or a dissecting kit or a way to watch the social lives of wolves.
Despite all of the aforementioned virtues, it is undeniable that insects will never fall into the category of what biologists call “charismatic megafauna”, the large showy animals like elephants and eagles that attract the attention of the public and help make the case for conservationists. When whales are endangered, people want to pass legislation and protest in storm-tossed boats. When the Quino checkerspot butterfly is endangered, people chuckle, and that’s if they are feeling sympathetic. Yet this seemingly innocuous, easily overlooked quality of insects, belying the extraordinary activity going on under our noses, is exactly what draws those of us in the know to them.
Insects are stereotyped as mindless automatons, operating on instinct. But recent evidence suggests that they have, if not the full range of personality types we see in humans, something that could be called “personality.” Insects can be bold or shy, and if they are bold under one set of conditions, like their inclination to come out of a shelter, they are also more likely to be aggressive to their fellows. The idea that behaviors come in suites like this has some important implications for how behaviors can evolve. And certainly this mantisfly, and the jumping stick insect, seem full of personality, not to mention charm.
More than 218,000 of the world’s 250,000 flowering plants, including 80% of the world’s species of food plants, rely on pollinators, mainly insects, for reproduction. According to some estimates, 15-30% of our diet in the United States relies on food sources requiring animal pollinators. In a typical fast food meal of a hamburger, fries, and a milkshake, most of the components required an insect somewhere along the way; although the wheat in the bun is wind-pollinated, the other plants, from the cucumber for the pickle to the feed eaten by the cow, are insect-pollinated. And researchers with the Forgotten Pollinators Campaign in Arizona calculated that one in every three bites of food is made possible by a pollinator. We tend to think primarily about honeybees when it comes to pollination, but honeybees are the plain vanilla of the pollinator world — they are well-known, but not as flashy or exciting as many of the others. Hundreds of other insect species help pollinate crops, including the blue orchard bee, the southeastern blueberry bee, and the squash bee.
Because I study sex in animals, people often ask me questions about how animal sexuality reflects that of humans. One of the most popular questions is about homosexuality in animals, and whether they ever exhibit it in the wild. The answer is yes, and even insects have sometimes been observed in same-sex pairs. Damselflies, for example, will occasionally form the characteristic “mating wheel” with two males. Genetic changes in fruit flies can produce males that court other males as well as females. But this doesn’t mean that they have a “gay gene,” or that human homosexuality is caused by genes. This is another case where just because a behavior in animals looks superficially like something in humans, we tend to lump the two together, even though our own sexual responses are far more complex.
Another stereotype about insects is that, other than honeybees and other social species, they simply lay their eggs and walk (or fly) away, with no parental care. But that too is a myth. I have never understood why nature shows on animal families are filled with images of doting monkeys nursing their infants, or diligent songbirds delivering a beak full of worms to the nest, when much more tender sacrifice takes place under leaf litter in the garden. If you want an ideal example of a good animal mother, for my money you can’t do better than an earwig. Now there’s a parent for you. After they lay their eggs, earwig mothers stand protectively over the clutch, scrubbing them clean of fungus and other nasty contaminants and keeping predators at bay. Other insects guard their eggs and young, and the mother may even digest the food first and then regurgitates it to her begging offspring, as if offering a squalling infant a bottle.
Learning happens in many kinds of animals, and in many different ways. Bees learn to find nectar by following their nestmates to a field of flowers, for example. But true teaching is a different story, requiring that an animal help the pupil while paying some price for the lesson, usually the time and effort required for the demonstration. Finding an occurrence of this narrowly defined behavior in nature has been daunting, and until very recently scientists had essentially no examples of real teaching by animals. Just within the last few years, however, researchers have found three cases of it — one in a bird, one in a mammal (the meerkat), and one, incredibly, in ants.
In at least one ant species, a single worker will actively recruit another ant to follow her to a food source or a new nest, or just to explore a new area, in a process called tandem running. The lead ant goes in front, while the follower keeps contact by tapping her with her antennae. If the follower gets behind, the leader waits for her to catch up. According to Ellouise Leadbeater and her Queen Mary University of London colleagues, “The intimate interaction between leader and follower in a pair of tandemly running ants at first sight bears all the hallmarks of a parent teaching a child to ride a bicycle.”