Black Widow Spiders in Ohio and California

Adult females are shiny black with a red, hourglass-like mark under the abdomen. The mark can vary and is rarely missing.¹ They are about 1/2 inch long in the body. Males are much smaller.^1,2

The young look different. Spiderlings hatch with tan legs and a white abdomen with black spots, then turn olive-gray or tan with white stripes.¹

In Ohio, a broken hourglass points to the northern black widow, and the northern female usually has a row of red spots on top.^2,3 The brown widow in California is smaller at about 3/8 inch and mottled tan, brown and gray. Its egg sac, with silk spikes, is the best clue.¹

The false black widow is chocolate brown and never has red marks.¹ See the spider guide for other look-alikes.

The female lays eggs in a yellowish, teardrop-shaped sac. A western sac holds about 300 eggs.¹ A northern widow sac holds about 250, and she can make up to nine in one summer.² Eggs hatch in three to four weeks.²

A female can make more than 10 sacs after one mating without fewer eggs or lower hatch rates.¹ Brown widow females can make 20 or more sacs in a lifetime, sometimes several at once.¹

Spiderlings can balloon on silk threads, traveling from a few feet to miles.¹ Only a small fraction survive.²

Females live longer than males.² Contrary to the myth, female widows rarely eat their mates after mating. They may if hungry.⁵

• A tough, cobweb-like web in a garage, near doors and vents, or in holes and crevices.¹
• Webs close to the ground, usually within three feet. Some are built higher and drop 10 or more feet.¹
• Yellowish teardrop egg sacs in the web. Brown widow sacs look spiky.¹
• Clutter, woodpiles, rock walls, barns and outbuildings, where they hide.¹
• Curled lips on toys, playhouses, picnic tables and plant pots.¹
• A spider that comes out at dusk.¹

The Ohio find at the base of a garage door frame fits the pattern.³

Bites are quite rare, even where widows are common, and most serious ones come from adult females.¹ The bite is often painless or feels like a pinprick. Symptoms often start within an hour.¹

Look for rigid stomach muscles, sweating, pain that spreads, and less often numbness, agitation or fever.¹ The CDC says the venom is a neurotoxin that can spread pain to the chest, abdomen or whole body.⁴ Symptoms often feel like the flu and fade within a few days.¹

Get medical care right away. A cold pack can ease pain.¹ Antivenom works against all tested black widows and can bring relief fast. It is made from horse serum, so doctors watch for allergic shock.¹

The brown widow venom is strong, but the spider is smaller and a bite is unlikely, since a disturbed one drops and plays dead.¹ Tetanus shots should stay current, because bites can become infected.⁴

This is mostly a clean-up job. Reduce clutter, woodpiles and heavy ground cover. Vacuum or sweep corners, windows and storage areas often, since vacuuming usually kills spiders.¹

You can hunt at night with a flashlight and kill them with a shoe or rolled newspaper. Or relocate them about 100 feet from the home using a jar and paper.¹ Wear gloves when you handle clutter, wood or outdoor objects.¹

Sprays do not work well alone. Insecticides do not give long-term control, and most registered water-based products had no significant effect on brown widow egg sacs in a 2016 study. Petroleum-based products did reach inside the sacs.¹

Complete elimination is not practical, and both species reinfest treated areas.¹ A pro can help with the hard places, but expect repeat visits. A Miami University researcher urges people not to kill them because they eat pests.³

A national spider cost guide gives an average of $400, with most jobs at $300 to $500.⁶ It gives no separate price for black widows, but says costs run higher for large venomous spiders.⁶

A single visit runs $125 to $350. Quarterly service runs $350 to $750 and monthly $600 to $1,250.⁶ Garages and basements run $400 to $1,000 per treatment, yards $150 to $450 and attics $170 to $500.⁶

Pet-safe products add roughly $100 to $200.⁶ Possible repairs afterward run $100 to $550.⁶

Because spiderlings drift in on silk and the spiders re-infest, a repeat plan can cost less over time than a single visit. Ask for two local quotes.

• Store garage items in zipper-lock bags or taped boxes raised off the floor.¹
• Wear gloves when you handle clutter, wood or outdoor objects.¹
• Check toys, playhouses, picnic tables and plant pots with curled lips.¹
• Keep outdoor lights away from walls and doors, because insects draw spiders.¹
• Reduce clutter, woodpiles and heavy ground cover near the house.¹
• Shake out clothing, shoes and towels before use.⁴
• Clear debris and trim tall grass around work areas.⁴
• Vacuum corners, windows and storage areas on a schedule.¹

Widows come out at dusk and stay near ground-level retreats.¹ Egg sacs build up over the summer, with a female making up to nine in a season.²

Spiderlings can balloon on silk at any time of year, so control has to be repeated throughout the year.¹

In Ohio, a female was found alone in her web on Sept. 14 with no egg cases, which was unusual, since egg cases are usually present at that time of year.³ Brown widows in Southern California are common in urban areas and parks.¹

Ohio has two black widows, the northern and the southern. The southern one is found in southern parts of the state.³ An Ohio State urban entomologist confirmed a northern widow in New Carlisle, Clark County, by its broken hourglass.³

He said there have been 250 reported sightings in Ohio, and the count may be low since widows are shy.³ A Miami University researcher says they eat agricultural pests and urges residents not to kill them.³

A person who applies pesticides to another party's property for pay needs a commercial applicator license from the Ohio Department of Agriculture.⁷ Category 10a covers general pest control.⁷

The western black widow, Latrodectus hesperus, is the most common harmful spider in California.⁵ It is common in deserts and in mountainous terrain above 5,000 feet in Southern California.¹

The brown widow is well established from Santa Barbara to the San Bernardino area and south to Mexico, as of 2016. Established populations had not been found north of the Los Angeles Basin, in the Central Valley or in the deserts.¹

The false black widow, Steatoda grossa, is common indoors in Pacific Coast homes. Its bite is like a yellowjacket sting.¹ The noble false widow was first found in Southern California in 2011.¹

The California Structural Pest Control Board has a Verify a Company or Licensee page for checking a pest company.⁸