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The Vampires of the Insect World: Ticks

If you’ve ever been for a long walk in a field of tall grass or an overgrown forest, chances are you’ve become the reluctant host of at least one tick, and probably many more. Ticks are one of the most reviled of all insect parasites, not just because they’ve become so ubiquitous in most parts of the U.S. (where about 90 of the 900 known species of ticks make their home), but also because they can transmit a large number of dangerous diseases to their animal hosts. Ticks can be divided into two primary groups – hard-shelled, which comprise the bulk of tick species, and soft-shelled, which are less common (and can be easily squished). All ticks belong to the Arachnida class, along with spiders, mites and scorpions (about 100,000 named species total).

Like other insect parasites, it takes a little extra effort to look beyond their negative reputation (no matter how well-deserved you think it may be) to understand their role as one more creature in the world’s vast ecosystem, and to understand the role they play in making everything, well, tick. So let’s get started – and where better to begin than with the lifecycle of these tiny critters.

The Lifecycle of Ticks

Most ticks follow the typical pattern of insect development: egg, larva, nymph, adult. It sounds simple enough, but to make it through every stage, ticks need to gorge on blood to provide themselves with the resources they need to grow and develop – a sort of macabre version of the LIFE® board game. In cooler areas, it can take three years to move from egg all the way to adult, and a good number die from starvation (or predation) long before that stage. In warm or tropical regions, the entire process can take no more than a year. In their larval stage, ticks tend to stick with birds and reptiles for sustenance, which means humans and other large animals are pretty safe. Its in the nymph and adult stages when ticks really begin to expand their circle of prey to include large mammals like humans. Between each stage, the tick molts (sheds its exoskeleton) to accommodate its new size and shape. Only one blood meal is necessary to move from one stage to the next. Once the final meal is consumed, female ticks drop from their host and lay thousands (yes, thousands) of eggs; males die soon after mating. (Interestingly, unlike female ticks, many male ticks consume very little blood, living only to pass on their genes before dying.)

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When it comes to finding a home, ticks tend to prefer damp, warm areas. They’re especially prone to drying out, so staying in areas with relatively high levels of humidity is important for their survival. Grown ticks also tend to like areas with a lot of high grass or brush that provides easier vantage points to find and latch on to prey, while tick larvae stay close to the ground where they find it easier to prey on small mammals and reptiles.

The Hostess With the Mostest

Now, it’s time to talk feeding. For this part, you have to leave behind the distasteful image of sneaky, evil ticks hunting down prey to feast on blood, and instead, recognize them as living creatures simply looking for what they need to survive and reproduce. After all, ticks aren’t out to annoy their hosts – they need them to live. It just so happens the relationship they share with their hosts can be, well, pretty bad for the host.

To feed, a tick relies on several key factors to identify a potential host: body warmth, body odors, moisture, CO2 from exhaled air and vibrations from movement – some ticks even respond to passing shadows. And to make their search easier, they exhibit a behavior known as “questing.” Questing begins by identifying a nice, study stalk of grass or other material, climbing to the tippy-top, and then spreading its arms out to make it easier to grasp animals as they walk past.

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Once on the host, a tick may find a spot and attach itself right away to begin feeding or it may wander around the host for a little while, looking for an area where the skin is thinner and easier to pierce. On humans, ticks are especially fond of warms areas like the groin, the thin skin behind the ear, along the neck and hairline, under the arms, in the creases of the knees and elbows, and even between the toes. Some ticks are so minuscule, they can resemble tiny, brown freckles.

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After it finds the best spot to feed, it pierces or cuts through the skin using long, tooth-edged rods called chelicerae that kind of look like tiny serrated knives. These rods are very flexible and they can be extended and withdrawn as needed. Once the skin is pierced, the tick can assess the odors emanating from the wound to determine if it wants to stay put or prefers to seek out a better location for feeding. So say this is a good spot; what happens next? The tiny, toothed chelicerae begin moving back and forth, using the serrated edges to snag the skin and dig deeper so the sucking portion of their mouths can be completely embedded. After this entry point has been well established (it takes about 30 strokes of the chelicerae to reach the right depth), the sharp tube-like portion called a hypostome is driven in (about six times to reach the best depth), and finally, the tick can begin to feed. The chelicerae remain extended to hold the tick firmly in place, and its these tiny teeth that can make removing a tick so difficult (unlike a mosquito that can be deterred with a simple finger flick).

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How do scientists know how many pokes and extensions it takes to drive a tick’s feeding tube to the right depth? Why, they’ve made a video, of course. You can see it right here, thanks to National Geographic. The video isn’t for the squeamish; but again, if you can separate yourself from the concept, it’s interesting to note how the tick’s mouthparts have evolved to support its need to hang on for the duration (ideally – at least from the tick’s point of view – for about a week), enabling it to consume its fill of blood so it can move on to the next stage of its life and eventually reproduce. (OK, it sounds creepy, but let’s face it – if we had mouthparts that enabled us to pierce the skin of a cream donut and easily extract the filling, we’d be all over it.)

Tick Spit

Of course, biting and digging in to a host is just one part of the tick-feeding story. The other and perhaps even more interesting part involves their saliva. Tick saliva is a very complex substance, with each the saliva of a single tick containing hundreds of proteins, some of which are only found in ticks. (In fact, taken together, tick species have thousands of different proteins in their saliva.) Scientists have determined what a few of these proteins do, but they still haven’t figured out the roles most of them play. Unsurprisingly, some of the proteins and other substances in tick saliva have evolved to make it easier for the tick to feed. For instance, like mosquito spit, tick saliva contains an anesthetic that keeps the host from feeling the tiny prick that occurs when the skin is pierced and while the tick is in position. Likewise, tick saliva contains anticoagulants that prevent clotting and encourage blood flow for easier feeding. And proteins aren’t the only things found in tick saliva …

How a Tick Can Make You Sick

Ticks are carriers of several dangerous microorganisms that can make humans (and other animals) very sick, and they transmit these pathogens through their saliva. In the U.S. alone, ticks are the primary vector (disease transmitter) for serious diseases like Lyme disease, Rocky Mountain spotted fever, Colorado tick fever, Q fever, human granulocytic and monocytic ehrlichosis, tularemia, relapsing fever and babesiosis. More recently, lone star ticks have been implicated in a serious allergic reaction to red meat that causes hives, swelling and even anaphylaxis, which in turn can cause shock and even death. And still more recently, researchers have been looking into tick transmission of the Powassan virus, primarily in the northern part of the U.S., and the Bourbon virus in the South (named not for the liquor, but for the Kentucky County where the virus caused a fatality in 2014). Another tick-borne disease, tick paralysis, occurs mostly in domestic animals (and sometimes in young children) when neurotoxins produced by female ticks enter the spinal column, causing muscle pain, loss of movement, convulsions and, eventually, respiratory failure. Some diseases are accompanied by “clues” like rashes or “bullseye” red spots (the telltale sign of Lyme disease infection), but often, these indicators don’t appear or occur in areas of the body where they’re less likely to be noticed, allowing the disease to progress without treatment.

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Is there anything good about ticks?

Most creatures serve a purpose beyond simply procreating; do ticks bring anything beneficial to the table? Yes – they provide a food source for many other creatures, including birds and even some mammals. In fact, one study found a single opossum consumes about 5,000 ticks each year on average simply through grooming. Ants, beetles, spiders, rodents and birds (notably guinea fowl and the African oxpecker) enjoy snacking on ticks, and, as demonstrated by the tick’s ability to host and transmit disease, many ticks serve as the unwitting host for a variety of bacteria and even some fungi. Recent research has focused on very tiny wormlike creatures called nematodes in controlling tick populations. In a real twist of irony, when preying on ticks, the nematodes transmit bacteria lethal to the tiny arachnids, giving the tick a little taste of its own medicine.

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The Final Word

Learning about insects is interesting, but it’s even more interesting when you can use what you learn to skeeve other people out. Here are a few interesting tidbits to help you in that goal:

  • Ticks will “drink” blood until they become bloated and engorged, giving rise to the idiom “fat as a tick” to describe someone who’s eaten a lot of food.
  • Ticks can survive underwater for 15 days, using a special kind of respiration to draw oxygen from the water.
  • You can’t remove a tick by covering it with petroleum jelly, spraying it with perfume or lighting a match near it. But you could wind up hurting yourself in the process. The best way to remove a tick is to use very slim tweezers to grasp the tick near the head, then extract it using steady pressure.
  • Some tick species are much more aggressive than others; for instance, deer tick bites can often be prevented by tucking in your clothing, including your pants legs, to provide a barrier that will turn the ticks away. Dog ticks, however, will just keep crawling on you until they find a place to bite.
  • Ticks don’t drop from trees, so if you find one on your scalp, it’s because it crawled up your body to get there.
  • Ticks don’t die off in the winter – however, they do become less active or dormant, which is why you’re far less likely to be bitten. Studies show in a freezer, ticks can die after a 24-hour exposure to temperatures of about -2°F (-19°C), but in their natural environment under a protective layer of snow, temperatures have to get a lot colder to be fatal.
  • As for heat, running your clothes through a washer set at at least 130°F (54°C) can kill ticks – but even just under that threshold, half of ticks will survive, according to one study. In the dryer, it takes nearly an hour on the high heat setting to kill ticks.

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Ticks are interesting to learn about, but they can be sources of very serious and even fatal diseases. Wearing light-colored clothing tucked in whenever possible and following up a walk through woods and fields with a close body inspection is the best way to spot ticks and remove them before they have a chance to spread disease. Don’t forget to check your pets too!