Spiders

These pests are outside the authority of the Vector Control Program. We offer educational information but do not control or regulate these pests. 

Not all spiders are harmful. In fact, most pose no threat to humans, and some spiders are helpful. Spiders rarely bite humans, and the bites usually do not break the skin. However, some venomous spider bites can cause swelling, tissue damage and disturb the function between nerves and muscles, which can lead to paralysis.

Venomous Spiders in the San Diego Area

Black Widow, Brown Widow and the Desert Recluse

Seek immediate medical attention for Black Widow, Brown Widow, or Desert Recluse spider bites.

  • Wash the bite mark with soap and water to help prevent infection.
  • Rub ice cubes on the bite to numb and reduce the pain.
  • For other spider bites, seek medical attention when necessary.

Children under the age of 6, people over the age of 60, and those with cardiovascular disease face higher risk from a venomous spider bite. An allergic reaction may cause circulatory failure. A bite victim may be kept under observation for 24 hours in case of an allergic reaction.

Black Widow spider and egg sac

Black Widow Spider

The adult female Black Widow spider has a venomous bite. The female’s abdomen is shiny, black, and round with a red hourglass figure on the underside. Adult females are about 1/2-inch long, not including the legs. The egg cases of black widows are smooth.

Adult male Black Widow spiders are harmless, about half the size of females, and their abdomens usually have red spots and white lines or bars.

Brown Widow spider and egg sacs

 

Brown Widow Spider

Brown Widow spiders are mottled tan and brown in appearance. Like the Black Widow, they have an hourglass figure on the undersides of their abdomens that is orange, rather than red. The egg cases of brown widows are bumpy. 

Desert Recluse

 

Desert Recluse Spider

The Desert Recluse (a different species than the Brown Recluse) lives in the Sonoran and Mojave deserts, the foothills of the lower Joaquin Valley, and areas close to the Mexican border. 

How to avoid spider bites

  • Wear shoes outdoors.
  • Do not reach into holes, under furniture or in woodpiles where you cannot see them.
  • Shake out clothing, towels, shoes, gloves, and boots before each use.
  • Use caution around outdoor toilets (favorite places for spiders).

Controlling Spiders

To keep spiders out of your home, take these steps:

  • Clean up woodpiles and leaves around the home.
  • Seal cracks on the house foundation, and around windows and doors.
  • Use a high-pressure hose to spray spiders on outside walls.
  • Be sure not to carry spiders into your home on plants and in boxes.
  • Vacuum or sweep windows, corners of rooms, storage areas, garages, and basements to help remove spiders and their webs.
  • Spraying insecticide may also keep spiders under control. Choose the product that is right for your home and follow the label instructions carefully.                         

To have a spider identified please bring the specimen to our office. 

Questions?

  (858) 694-2888

  vector@sdcounty.ca.gov

 

Desert Recluse photo by Lynette Elliott