The pallid swift (Apus pallidus) is a small bird, superficially similar to a barn swallow or house martin. It is, however, completely unrelated to those passerine species, since the swifts are in the order Apodiformes. The resemblances between the groups are due to convergent evolution reflecting similar life styles. Swifts have very short legs which they use only for clinging to vertical surfaces. The genus name Apus is Latin for a swift, thought by the ancients to be a type of swallow with no feet (from Ancient Greek α, a, "without", and πούς, pous, "foot"), and pallidus is Latin for "pale". They never settle voluntarily on the ground. Swifts spend most of their lives in the air, living on the insects they catch in their beaks. They drink on the wing.