Annotated checklist of the diplura (Hexapoda: Entognatha) of California.

The first checklist of California dipluran taxa is presented with annotations. New state and county records are reported, as well as new taxa in the process of being described. California has a remarkable dipluran fauna with about 8% of global richness. California hosts 63 species in 5 families, with 51 of those species endemic to the State, and half of these endemics limited to single locales. The genera Nanojapyx, Hecajapyx, and Holjapyx are all primarily restricted to California. Two species are understood to be exotic, and six dubious taxa are removed from the State checklist. Counties in the central Coastal Ranges have the highest diversity of diplurans; this may indicate sampling bias. Caves and mines harbor unique and endemic dipluran species, and subterranean habitats should be better inventoried. Only four California taxa exhibit obvious troglomorphy and may be true cave obligates. In general, the North American dipluran fauna is still under-inventoried. Since many taxa are morphologically uniform but genetically diverse, genetic analyses should be incorporated into future taxonomic descriptions. Natural Heritage Program conservation status ranks were recommended.