Why you can't flick a tick

Why can't you flick a tick off you or your pet's skin? The answer is in the tick's mouth that's covered with hooks evolved so the tick can hang on for a several day feast of delicious blood. From KQED's Deep Look:

...A tick digs in using two sets of hooks. Each set looks like a hand with three hooked fingers. The hooks dig in and wriggle into the skin. Then these hands bend in unison to perform approximately half-a-dozen breaststrokes that pull skin out of the way so the tick can push in a long stubby part called the hypostome.

Its almost like swimming into the skin, said Dania Richter, a biologist at the Technische Universitt Braunschweig in Germany, who has studied the mechanism closely. By bending the hooks its engaging the skin. Its pulling the skin when it retracts.