Here's What Happens When A Tick Bites You - National Geographic

When a tick wants to bite, it starts by gently coursing its chelicerae over the skin of its host (at about 0:25 in the video). Each one ends in a tooth that’s tapered to an especially sharp point, which scrapes and punctures the skin with very little force. This also releases smells and other chemical information that the tick can weigh up.

Now, it’s time to break in (1:35 in the video). The chelicerae start to flex their tips. At first, they take turns; eventually they move together. With each sweep, the teeth snag on the host’s flesh and bury the chelicerae even deeper into the skin. After 30 of these movements, the entire tips are firmly embedded.

The tick then contracts both of its chelicerae while flexing both tips, like it’s doing a nightmarish version of a breaststoke (2:20 in the video). The motion drives the rigid, sword-like hypostome into the skin, and the backwards-facing spines keep locked in place. The chelicerae relax and extend, before flexing and retracting again. Each stroke ratchets the hypostome deeper and deeper. After six of them, it’s completely buried and the tick starts to feed.

This is a very different sequence of events to what happens when a mosquito bites you (and you can watch a video of that too). That’s because ticks, unlike many other blood-suckers, are adapted for the long haul. A mosquito bites, sucks and quickly leaves. A tick bites… and stays there for days. It needs to attach itself very firmly so that it can’t be easily dislodged. It does so with the curved teeth and spines on its mouthparts, and by burying them very deeply.

The same sticking power is also vital for the parasites that ride inside ticks, like the spirochete bacteria that cause Lyme disease. They only spring into action when the tick starts feeding, and they need to time make their way from the creature’s guts into its bloodstream, into its salivary glands, and finally into its host. The whole process can take a couple of days. If the tick wasn’t so good at anchoring its face into a host, Lyme disease wouldn’t exist.