There are not many species of spiders in California that have a lethal bite, among them we can name the black widow and the brown recluse spider.
The black widow has a very toxic poison that acts in the nervous system. Fortunately, the quantity of poison this spider injects is small; Besides, is a very elusive species, and in general, does not like living near human beings. The bite of the black widow can be treated and is rarely mortal.
The lonely brown recluse spider or "violin spider" (recluse loxosceles) does not live in California, but in the South of the State; at the base of the mountains in the Sonora and Mojave deserts, lives a close relative of them, the Loxosceles deserta. Is a very elusive specie that avoids the contact with human beings, although sometimes, we can find it in our homes, specially in dry and isolated places, such us attics, closets, garages and places used to store objects during long periods. Other specie is the Loxosceles laeta, with its roots in Southamerica, was found for the first time in Los Angeles in 1969, but its arrival is unknown. The brown recluse spider’s bite causes many types of reactions.
The bites of the black widowed like the bites of the brown recluse spider are in general painless, what makes us to ignore them. In a few hours, the bite starts to hurt and the skin inflates. The victim can also show nauseas and slight general pain. Just in a few cases the brown recluse spider’s bites can get infected and cause temperature, or destroy the red corpuscles and, eventually, a surgery in the affected area must be needed. In serious cases of black widowed’s bites, some people can suffer from breathing problems and perspire. However, both bites have slight consequences and the symptoms decrease on their own in a few days.
As quoted from brownrecluse.org HAH! In your face Spiderman!
Cheers, TB.