What makes a Poison-dart Frog poison?

Dendrobates azureus exudes a toxic secretion like the other members of its family. None of the frogs make the poison they "wear" on their skins but get it from what they eat. Of the variety of insects and such in their diets, it is the ants and mites that actually manufacture and carry the toxins - until the frog eats them and "borrows" their poison. Wikipedia has more information, and you've got links.