They are found in the southern United States and Mexico: H. theologus is mostly found west of the Colorado River, while H. selenopoides is mostly found to the east, with some populations in Death Valley and near Mercury, Nevada.
The species are located in the southern United States and Mexico.  H. theologus is primarily found west of the Colorado River, whereas H. selenopoides is more common to the east, with a few populations in Death Valley and near Mercury, Nevada.