Not as many as one would think as they like to hide in dark places. You can find them most anywhere in warm desert climate and don't usually bite people unless the have been surprised. Ie. Hiding in a shoe and not checking shoe before putting on. Only a few dozen people are bitten a year and there is an antivenom available, but you can only take once in a lifetime. If you live somewhere like arizona or warm desert like conditions, always check inside you shoes before putting them on
