In western North America, the milliped order Callipodida is represented by the Colactidini, Tynommatini stat. n., and Diactidini tribus n., in the subfamily Tynommatinae, family Schizopetalidae; a coordinate tribe, the Texophonini, occurs on the Gulf Coast of south Texas. The Tynommatini consists of two genera and four species: Tynomma mutans (Chamberlin), T. magnum Buckett & Gardner, and T. gardneri sp. n., occurring around Monterey and San Pablo/San Francisco Bays, California, and Idrionaria dineh gen. n. & sp. n., in Washington County, Utah. The Colactidini ranges from Durango, Mexico, to central Utah and California east of the Sierra Nevada, with disjunct areas in southern California and Baja California, the latter extending northward to metropolitan San Diego. It is represented by two genera and 6 species: Colactis Loomis: C. tiburona (Chamberlin), utorum (Chamberlin), and protenta and quadrata, both by Loomis; and Heptium Loomis: H. carinellum and scamillatum, both by Loomis. The Diactidini, occupying coastal southern California and the adjacent fringe of Baja California, is comprised of three genera and 10 species: Diactis Loomis: D. soleata, triangula, and frondifera, all by Loomis, and amniscela, cupola, jacinto, procera, and strumella, all spp. n.; Florea sinuata gen. n. & sp. n.; and Caliactis bistolata gen. n. & sp. n. The following new synonymies are proposed: C. yuma Chamberlin, sideralis Loomis, and loomisi Hoffman under C. tiburona; C. briggsi Shear and saxetana and baboquivari, both by Loomis, under C. utorum; H. canum Chamberlin under H. carinellum; and Etiron paroicum and pearcei, both by Chamberlin, under D. triangula and T. mutans, respectively. The eastern Nearctic callipodid fauna is summarized and significant new localities are reported; Tetracion antraeum Hoffman, stat. n., is elevated from a subspecies of T. jonesi Hoffman.