CERTHIA, in ornithology, the CREEPER or OX-EYE, a genus belonging to the order of PICÆ. The beak of this genus is arched, slender, sharp, and triangular; the tongue is sharp at the point; and the feet are of the walking kind, i. e. having the toes open and unconnected. There are 25 species, of which only the familiaris, or common ox-eye, is a native of Britain. It is grey above, and white underneath, with brown wings and ten white spots on the ten prime feathers. It creeps up trees; lays about 20 eggs; and feeds upon caterpillars, and the eggs of insects.