Photo: Sakai Yuji/Getty Images

Why let creepy clowns get all the attention? From now until Halloween, Science of Us is investigating the psychology behind some of the most common fears.

In a 2013 interview with Popular Science, ecologist Jeffrey Lockwood, author of The Infested Mind, recalled a time when he found himself caught in a massive grasshopper swarm: “I had worked with insects for years and grasshoppers for a very long period,” he said, “but [in this instance] their numbers and behavior and their overwhelming capacity conspired to generate a panic attack, which was extremely disturbing for me. I’d never had such a reaction to insects, or to grasshoppers in particular, until that time.”

Even a guy who makes his living studying bugs, in other words, is not immune to their strange, terrifying power. And it is strange: We know, rationally, that most of these tiny creatures can’t hurt us, and yet we shriek when they land on our skin, give them prominent roles in our horror movies, and spend a ton of time and money to rid them from our homes. There’s an entry in the DSM-5 for an extreme fear of insects — it’s called entemophobia, and can be treated with cognitive behavioral therapy — but even when it hasn’t reached pathological levels, the fear is real and widespread. In Chapman University’s 2016 Survey on American Fears, 25 percent of respondents said they were afraid of insects and/or spiders. That’s more than the number of people who feared becoming the victim of a violent crime, germs, or even dying. Why is something so small and harmless considered so scary?

Because some of them are actually dangerous.

To be fair, insects aren’t always so innocent: Some of them bite or sting. The Zika epidemic over the past year has been an acute reminder that they can carry devastating diseases. And this potential of a few species to cause harm, some scientists believe, may have ruined things for the whole bunch — that our fear of things that creep and crawl is an overly cautious, but hardwired, form of self-preservation. In one 2001 study, for example, the study’s authors showed volunteers pictures containing elements that were either threatening (spiders and snakes) or neutral (mushrooms and flowers) and asked them to locate the target object within the photo. Overall, the participants spotted the spiders and snakes much more quickly than anything else; those who had previously indicated on a questionnaire that they were afraid of either species proved especially speedy at homing in on them.

The researchers used the results to argue that we’ve evolved to be especially attuned to the presence of potentially dangerous animals, however small: “Certainly there are certain stimuli that are pre-wired in the brain because they have been perennially dangerous to our ancestors,” lead study author Arne Öhman, a psychologist at Sweden’s Karolinska Institute, told National Geographic at the time.

Because we find them disgusting.

But we aren’t just afraid of insects the same way we would fear other dangerous animals, like lions or bears. There are plenty of species that we’d run from if we saw them in the wild, but that we have no qualms about making into cuddly animated characters — but there’s a reason we don’t have bugs gracing the covers of our cereal boxes or appearing as lovable heroes in our kids’ cartoons: The fear of insects is a more complicated fear, one that’s tightly bound up with feelings of disgust.

Psychologists studying disgust talk about something called the “rejection response” — the overwhelming feeling that you need to get this thing away from you, like, right now. Disgust is shaped in part by culture, but it also has its roots in biology, and the rejection response, like fear, is a mechanism designed to keep us safe: We’re disgusted by feces and rotting food, for instance, because each has the potential to make us sick. Along those same lines, the presence of insects often indicates that something isn’t safe to consume or touch. Over time, we’ve come to associate the messenger with the threat itself.

Because they look weird, or there are too many of them, or they trespass on our turf, or …

There are other theories, too. Some researchers believe insects are terrifying mainly because their physical forms are so unlike our own — skeletons outside their bodies, a skittery way of moving, too many legs and too many eyes. Others have argued that their sheer numbers stir something deeper inside our psyches: The Jungian psychologist James Hillman, for instance, has argued that a swarm of insects “threatens our fondly cherished human notions of individuality and independence … Imagining insects numerically threatens the individualized fantasy of a unique and unitary human being … [and] indicate insignificance of us as individuals.”

In his Popular Science interview, Lockwood offered up another idea: These days, most of us see insects primarily as uninvited guests. “Now that we’ve moved into urban environments where close quarters and hygiene are at a premium,” he said, “we find that the vast majority of our interactions with insects are negative in that they are the things that are invading our homes and our private spaces,” rather than things we see out in nature. Most of the time, then, an encounter with a bug will feel like an invasion — like an encroachment on our home territory, a place where we’re supposed to feel safe and clean and in control. They may be tiny, but they’re packing some hefty symbolism. It’s a contrast that, come to think of it, sums up most of the theories on their fearsomeness pretty tidily.