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After about an hour in the forest with Clow, I stop for a periodic inspection of my blanket and, right near the top, heading with surprising speed for the handle (and my bare hand) I see something? “Katie,” I ask, “is this a tick?”
Clow hurries to me, leans in for a look, and lights up like Christmas morning. I have picked up an adult female blacklegged tick, with a black hood on a handsome dark-red scutum. A short while later, Clow finds a tick on her own blanket and is equally pleased: you’d never guess she has encountered 10,000 ticks in her professional life. She identifies it another I. scapularis then sets it gently down on a leaf so I can have a good look. The tick immediately scooches to the end of the leaf and begins to wave its front legs back and forth.
“Ooh,” Clow croons. “She’s questing!”
A questing tick waits at the end of a blade of grass or leaf, with its legs outstretched, tracking the changes in heat and CO2 that signal that something biteable is walking by, poised to jump aboard a sort of arthropod hitchhiking. Watching Clow watch the tick, I recognize the phenomenon that I saw in Robbin Lindsay and every other tick expert I talked to: the admiration for ticks, for their adaptability and ingenuity and complexity.
A tick can live for a few years without feeding. But, like a video game vampire, they need blood a “blood meal,” as it’s known in the zoology world to level up and move between stages of the life cycle. They start out as eggs, typically laid in the leaf litter on a forest floor. (But some, like the brown dog tick, will deposit eggs in a convenient crevice in your floor.) The eggs hatch into larvae, with just six legs, usually in late summer, although the seasonal timing varies between ticks. And thus begins the hunt for a host a reptile, bird, amphibian, or mammal that will provide the blood that will allow them to mature. When the larvae have fed on something small, they drop back to the ground and moult, becoming a nymph. They will overwinter, burrowing under the leaf litter to keep warm. As nymphs, they develop that last set of legs, and at this stage, they can host many pathogens. When the next blood meal happens, typically off a larger creature, they are able to be infected with bacteria or viruses and to pass them on, when they feed again, as an adult. Nymphal ticks are tiny, and thus much harder to spot and remove, so they’re the ones most likely to get away with making their way inside your trousers and having a long feed. After the nymph moults again to become an adult, it quests its way onto a larger host, such as a dog or a deer or a human. Males and females meet and mate on a host before dropping off; some species lay several thousand eggs in a process that can take weeks. If a female doesn’t find a host to reproduce on in the fall, she burrows back into the leaf litter and waits for spring.
 Katie Clow drags for ticks in November 2019
It’s a risky requirement, this need to feed on an exponentially larger and faster-moving host, when you’re a slow-moving creature the size of a sesame seed. And it’s the range of ways that ticks have found to navigate that risk that seems to make the tick people really excited. I asked Nick Ogden, a soft-spoken man from the north of England who emigrated to Quebec after studying Lyme disease at Oxford, why he chose ticks when he was starting out as a veterinary scientist given that he had his choice of creatures great and small. He started off casually but, in seconds, had revved up into a full-throated praise song:
They’re just amazing, amazing parasites. They are immensely tenacious. You find ticks pretty much everywhere in the world, in a whole lot of different ecological niches to which they have adapted themselves. Their whole biology is fascinating, how they sense hosts around them by being able to smell the CO2 we produce and the other kinds of pheromones that we’re producing. Then there’s their whole feeding thing: everyone thinks it’s like mosquitoes, that they’re just like a syringe, but they’re fascinating! They dig a hole in us, they bury their heads in, and they feed for up to two weeks. The mouthparts of an adult female tick are about the size of a splinter. The first thing that you feel with a splinter is that it hurts. And the first thing that you feel when a mosquito bites you, either it hurts or it stings. But you don’t know the tick is there!
A tick can coat its body in its own saliva, a liquid salty enough to pull moisture from the atmosphere. That is sustenance enough to keep it going for months or even years while it’s waiting for a meal. The saliva is produced in glands that can occupy as much as a third of the tick’s body cavity, and when it is time to feed the most dangerous time in a tick’s life this liquid is its primary defence mechanism against a host’s immune system. When you stroll by and a questing tick makes the successful leap, it attaches in one of two ways: by transuding a sort of glue to keep its mouth in place, or, as with the blacklegged tick, by poking barbed mouthparts into your flesh. When a tick bites, it begins by secreting enzymes that destroy a circle of flesh and create a tiny puddle of blood, which it begins to suck up. (A tick takes in blood and sends out saliva in alternating cycles.) The tick needs to kill pain so you won’t realize it’s there and flick it off. And it needs to stop your body from mounting the immune response that it would otherwise send against this intruder from the moment its mouthparts pierce your skin. Among the 3,500 proteins identified in the saliva of various ticks, some stop the molecules carrying a pain signal, while others are vasodilators, to get the blood flowing, or anticoagulants, to keep it from clotting. Some proteins stop the histamine response, which would make the bite itch and clear a path for immune cells to reach the site. There are also molecules that inhibit white blood cells. And, because the tick needs to keep feeding for days keeping your immune system fooled it changes up the protein composition of its saliva, like a dash into a phone booth for a new disguise.
So there you are, with a tick feeding and passing pathogens into your body after having disarmed your immune system. It’s the ideal situation, Ogden says, for a virus or bacterium looking to fulfill its evolutionary obligation by finding new animals to infect. “If a bug has to get from an arthropod into a host, what a wonderful gateway it is, where the tick’s feeding.”
Ticks like their tissue soft and thin, as Eric Stotts can tell you. Last October, Stotts went on a guys’ weekend to a cabin near Port Mouton, on Nova Scotia’s south shore, a couple of hours from his home, in Halifax. An affable forty-eight-year-old architect, Stotts goes with his buddies every year, and in addition to a lot of eating and drinking, they always take on a project and learn a new skill that someone in the group can teach. Last fall, it was filmmaking, and Stotts spent much of the weekend crouching and lying on the forest floor as he filmed long still shots of the last dark yellow leaves on the trees aiming for what he called a “kaleidoscopic” nature effect. He thought his film turned out pretty well, and when he was back in his home office on Monday, he was feeling good about things.
Until he went to pee.
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