Bugs and spiders in California

What to watch for in California

Two widows are established in California. The western black widow turns up in garages and crawl spaces, where adults and young can overwinter. The brown widow is mainly a spider of the urban south, and its bites are usually much milder, though it is easy to confuse with a young black widow. In the southeastern desert the Arizona bark scorpion is established as well. A sting is very painful and can be dangerous for young children and older adults, so call Poison Help at 1-800-222-1222.

Several ticks are established here. The western blacklegged tick is established in nearly every county and can spread Lyme disease and anaplasmosis. The Rocky Mountain wood tick lives east of the Sierra. The brown dog tick mostly lives indoors with dogs and can breed inside. Remove any attached tick promptly. American dog tick records exist, but it is not known to be established in California.

Through the year

Spring

Pill bugs and rough sowbugs show up after rain, and western blacklegged tick nymphs are most active, peaking in mid to late spring in northern California.

Summer

Argentine ants, American cockroaches and mosquitoes are most noticeable, and brown widows become easier to spot from summer into fall.

Fall

Asian lady beetles move in during October and November alongside brown marmorated stink bugs and western conifer seed bugs, while spotted orbweavers leave big webs up in daylight.

Winter

Western black widows can overwinter in garages and crawl spaces, house centipedes get noticed more often indoors, and Indianmeal moths are most often seen from November through February.