Philip Ward‘s A synoptic review of the ants of California” says there are two species within California. To quote from that source: “Ants in the genus Amblyopone (=Stigmatomma) have cryptic foraging habits and are specialist predators on geophilomorph centipedes and other arthropods living in soil or rotten wood. Two species are known from California: A. oregonensis (Wheeler) is found in shaded, medium-elevation coniferous forests in northern California, while A. pallipes (Haldeman) is widespread in chaparral and low elevation woodland.”
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These were collected in Tuolumne City area: