There are two non-native species in North America. The Mediterranean recluse is a worldwide tramp species. It has been reported in many locations around the country; however, a typical infestation is large in number yet restricted to one to several buildings. The exception is in central Washington DC, where they’re fairly common.
Finding a population in one building doesn’t necessarily guarantee they’ll be found in nearby structures, unless the structures are connected by underground passageways such as pipe conduits or steam tunnels.
Except on very rare occasions, Mediterranean recluses have never been found outside buildings in the U.S. These spiders look very similar to brown recluses, and are frequently misidentified as such.
Another species of recluse spider from South America has stable populations in a few cities in urban southern California — and a few museum basements elsewhere — but its is neither widespread nor known to bite people, despite residing in heavily populated areas of southern California for more than 70 years.
Check in next Moday for part 3 of the Brown Recluse