Genus Monomorium Mayr

California appears to have a single indigenous species of this genus, M. ergatogyna, a ground­nesting species which is widely but patchily distributed throughout the state except at high elevations. The reasons for treating M. wheelerorum as a junior synonym have been discussed above (under “Taxonomic Changes”). The introduced Pharaoh’s ant, M. pharaonis (Linnaeus), is a frequent pest in buildings in urban California. A second introduced species, similar to M. pharaonis but with a more elongate head and more shagreened sculpture, has been collected once in the state (images and locality information on AntWeb).

Species identification: keys in Wheeler and Wheeler (1986g). Additional references: Adams and Traniello (1981), Andersen et al. (1991), Berndt and Eichler (1987), Bolton (1987), DuBois (1986, 2000), Fernández (2005), Heterick (2001), Jones et al. (1982a, 1982b), Knight and Rust (1990).