Here's what you might not know about these banes of childhood: Though other species of lice infest other mammals and even birds, Pediculus humanus capitis lives on the human scalp and nowhere else. A louse spends the first week or so of its life as an egg, or nit, before hatching into a nymph. Over the course of about seven days, the nymph will molt three times, growing bigger each time, until it reaches the adult stage.

This Peruvian caterpillar reacts to loud noises with the tentacles on its back. 

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The Bombardier Beetle creates an internal explosion to propel hot, poisonous chemicals at its enemies.  Scientists studying the beetle have shown how it works in an x-ray video of the process.