The "spiny-tailed fairy shrimp," as Creaser (1930) referred to Streptocephalus seali Ryder, has been recorded from seventeen states in all sections of the United States, as well as from Canada and Mexico. Although it is probably the most widely distributed of all the North American fairy shrimps, it remains one of the least known. Extensive ecological and life history studies have been carried out by several investigators on various species of other genera. Probably these widely known studies are the source of the frequently encountered statements to the effect that fairy shrimp are cool water dwellers, appearing in temporary pools only during the early spring months and then disappearing until the following spring. Such statements, while generally true of many species of fairy shrimps, especially of the genus Eubranchipus, have no validity for the North American streptocephalids. In an earlier publication (Moore 1951) the writer presented observations on the the biology of S. seali based on eight months' field and laboratory studies. At the present writing several of the field stations have been under regular and frequent observation for over two years. Certain earlier conclusions may now be supplemented by additional data, and observations on the seasonal activities and growth rates of the species throughout the entire annual cycle are now available.