WHEN we consider the great variety and extent of adaptation among the insects, and especially when we recall the multitude of aquatic and semi-aquatic species, it seems rather remarkable that none of them has been able to take up marine life. Halobates, one of the Hemiptera, is truly oceanic, a few species of Diptera are known to live in sea water during their larval stage, a few larval forms have been found below high tide where they would be exposed to the sea water for a portion of the time, and a number of adult insects, chiefly beetles, range the shore finding their food when the tide is out. In brackish water, however, many species are regularly found, belonging to nearly all the insect orders. It is a noteworthy fact that nearly all of these are more commonly found breeding in fresh water and are not peculiar to brackish water conditions. While the occurrence of dragonfly nymphs in brackish ponds must have been noticed many times by observing naturalists; references in literature are exceedingly scant. Mr. E. A. Schwartz ("Preliminary Remarks on the Insect Fauna of the Gt. Salt Lake, Utah," Cad. Ent., vol. 23), found nymphs living in a mixture of salt and sulphurous or fresh water about Gt. Salt Lake, but adds: "The same species were also seen at Utah Lake, which is fresh water"; and the eminent authority on the dragonflies, Dr. P. P. Calvert in his " Catalogue of the Odonata of the Vicinity of Philadelphia" (Trans. Amer. Ent. Soc., vol. 20, 1893) makes the