Nine strains of herpetomonads have been isolated in pure culture from eight varieties of insects, and three strains from two species of plants. Four of the cultures were derived from latex-feeding insects (Oncopeltus fasciatus, Oncopeltus sp. ?, Lygaeus kalmii) and three from latex plants (Asclepias syriaca, Asclepias nivea), two from mosquitoes (Culex pipiens and Anopheles quadrimaculatus), on...