The true flies are those which have have only one pair of wings. Although nearly all other flying insects have four wings, in the true flies the hind wings have become modified into a pair of small balancing organs called halteres. A large number of flies are excellent mimics of bees and wasps (such as the hover flies, which have their own gallery) but, in addition to the number of wings, can be distinguished from them by their large eyes and short antennae.