Abstract does not appear. First page follows. Introduction Contemporary acarologists accept Stigmaeus(Koch, 1836), in the restricted sense first used by (Berlese (1910)).3 There is, however, a problem involved in this usage. Stigmaeus was one of the three genera originally included in the Raphignathidae. Neither the first reviewer of this family (Berlese, 1910) nor the second (Oudemans, 1923) was acquainted with the type species of Stigmaeus. During the period 1836-1841 Koch proposed five species in Stigmaeus of which the first two, cruentus and megacephalus, appeared in successive numbers of the same fascicle (1836). He did not designate a type species. It appears that no one specifically referred to S. cruentus K. as the genotype until (Berlese did so (1910), p. 205). This species was known to Berlese only by Koch’s description, and others since that time have been unable to identify it. (Berlese (1910)) attempted to rectify the matter by proposing a new species of his own authorship, S. rhodomelas(Berlese, 1910), as type species of a subgenus Stigmaeus (Stigmaeus). It is desirable to conserve this generic name because it has been perpetuated in the coinage of the family name, Stigmaeidae Ouds., 1931, and in a number of other generic names. The characters ascribed to Stigmaeus by (Berlese (1910)) are compatible with the general features of Koch’s illustrations of cruentus (1836, fig. 4.9; 1842, fig. 26). The expedient adopted for present purposes is to recognize cruentus as the nominal type species and to follow the definition of the genus proposed by (Berlese (1910)) and later by (Oudemans (1923), (1927). Most of the species of Stigmaeus examined by the present writer are undescribed species recovered from soil samples taken mostly in the western United States. Only three of these are recognized as species previously described from Europe: eutrichus Berl., antrodes Berl., and sphagneti (Hull). The identification of sphagneti (Hull) rests upon tenuous clues afforded by