Summary.
A general review is given of our present knowledge concerning marine midges in various parts of the world. These belong to several genera, and appear to have been derived from different branches of one tribe (Orthocladiariae) of the family Chironomidae. Some of the flies remain unmodified and may be found flying over rocks and seaweed; others have vestigial wings in one or both sexes, and these are found only at extreme low tides running on exposed rocks or over the surface of pools; none are truly submarine. The larvae of these various species occur in all tidal zones, sometimes even those below the limit of exposure by the lowest tides. Among these species two new ones are described from British coasts and one from East Africa.
Four new marine species are described from Samoa. One of these is known only from adult males captured on the wing, and belongs to the genus Clunio, hitherto believed to be solely European. The other three, of which both larvae and adults were obtained, belong to a different tribe (Chironomariae), and were taken among Halophila, a higher plant which grows in sea water on the reef. Two of these are normal air-living flies, and are referred to the genus Tanytarsus. The third is submarine in all stages, and shows remarkable structural adaptations to this life. The male has greatly reduced wings and bare antennae; it swims actively with its long legs. The female is without antennae, mouth-parts, wings, halteres, or functional legs, the front legs not even existing as vestiges. This submarine insect is described as a new genus and species, Pontomyia nutans, and reasons are given for believing that it has been derived directly from one of the species of Tanytarsus with which it is associated.