Rocky Benoit, MD

Red imported fire ants (Solenopsis invicta) were introduced into the United States in the 1930s by ships from South America that docked in Mobile, Ala. Fire ants are now active throughout the southeast Sunbelt states. Colonies are also found in California; one of the largest is in Orange County.

Patients stung by fire ants instantly feel intense burning pain at the site, hence the name "fire" ants; the small pustular lesions typically develop about a half hour afterward and evolve over several days.

The bites of only a few spider species produce medically significant effects in humans.