Diptera is an order of insects that contains true flies. Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced mechanosensory organs known as halteres, which act as high-speed sensors of rotational movement and allow dipterans to perform advanced aerobatics. This order is estimated to contain 1,000,000 species, although only about 125,000 have been described. Diptera is one of the major insect orders and of considerable ecological and human importance. Flies are important pollinators, second only to Hymenopterans. Flies may have been among the evolutionarily earliest pollinators responsible for plant pollination. (Wkipedia, Tree of Life Web Project)