The Holarctic chilopod subfamily Plutoniuminae Bollman, a corrected name for Plutoniinae, consists of two genera, Plutonium Cavanna and Theatops Newport, and six species; synapomorphies between them show that the subfamily is a monophyletic group and that the different number of spiracles, 19 pairs in Plutonium and 9 pairs in Theatops, is only a generic-level character. Plutonium and P. zwierleini Cavanna occur in Sicily, Sardinia, Napoli and Sorrento provices in mainland Italy, and Granada Provice, Spain. Theatops erythrocephalus (C. L. Koch) occurs along the eastern side of the Adriatic Sea in the Balkan Peninsula and in coastal Spain and Portugal. The other four species--T. posticus (Say), T. spinicaudus (Wood), T. phanus Chamberlin, and T. californiensis Chamberlin--occur in the United States and northwestern Mexico. Theatops posticus occupies a broad area east of the Central Plains from Connecticut and southern New York to the south Florida keys and eastern Texas; an allopatric western population extends from southwestern New Mexico and western Chihuahua to the southern Great Basin, the California desert east of the Sierra Nevada, the Pacific Ocean in Baja California Norte, the Channel Islands off the southern California coast, and the eastern slope of the Coast Range near the latitude of San Francisco Bay. Theatops spinicaudus occurs sympatrically with T. posticus in two areas of the east; the inner surfaces of its caudal legs possess variable series of ridges and teeth. Theatops phanus occurs in epigean and subterranean environments in southern Texas and extends from east of highway I-35 to west of the Pecos River; the inner surfaces of its caudal legs also possess variable series of ridges and teeth. The distribution of T. califoniensis, anatomically convergent with T. erythrocephalus, is as described previously, but locality information is detailed, as only one site, the type locality, is currently known. Relationships among the plutoniuminine species are postulated as P. zwierleini + (T. spinicau-dus + (T. phanus + (T. erythrocephalus + (T. posticus + (T. californiensis)))). The Plutoniuminae and Cryptopinae logically share ancestry, and the Scolopocryptopinae may warrant elevation to family status.