"Bowtruckles," said Hermione. "They're tree-guardians, usually live in wand-trees. They eat woodlice, though they prefer fairy eggs. Whenever you need leaves or wood from a tree in which a Bowtruckle lodges, it is wise to have a gift of woodlice ready to distract or placate it. They may not look dangerous, but if angered they will try to gouge at human eyes with their fingers which are very sharp."