Poisonous Spiders in Ohio

Almost all spiders Ohioans are likely to come across in their gardens and yards are venomous, but almost none of the species possess venom strong enough to be a threat to humans. Only a few kinds of spiders in Ohio are potentially dangerous, and even they rarely pose a significant danger to healthy adults.

Two species of widow spider, the black widow (Latrodectus mactans) and the northern widow (Latrodectus variolus), are in Ohio. Both species are moderate in size, with the female reaching up to 1/2 inch in body length. The females are dark-colored and have a distinctive bright-red, hourglass-shaped marking or two red marks on the underside of their abdomens.

Widows spiders build their webs away from human activity. Black widows often hide in abandoned or rarely used buildings, and northern widows often build their webs under rocks and logs.

Widow bites are usually immediately painful, and as the toxin in the venom takes effect over several hours, it can cause severe pain, muscle spasms and shortness of breath. Bites are rarely fatal in healthy adults, but they can be dangerous for children, the elderly and people with compromised health.

Two species of recluse spider, the brown recluse (Loxosceles reclusa) and the Mediterranean recluse (Loxosceles rufescens), are also sometimes found in Ohio. They are medium-sized, with a body length between 1/4 and 1/2 inch, and they are light brown with a darker, violin-shaped marking on their backs.

Recluse spiders are, as their name suggests, reclusive and shy away from human activity. They tend to hide in dark areas, and in Ohio they have been found only inside or close to buildings, which suggests they might not be able to survive outdoors during cold weather.

A recluse spider bite may not be painful at first, but pain may develop later. In the days after the bite occurs, the toxin in the venom may cause tissue around the bite to die, and a slow-healing ulcerated sore may develop.

Spiders of some other species in Ohio may occasionally bite humans. Although the venom of those spiders rarely causes a severe reaction, individuals with particular sensitivity to it may experience symptoms such as pain and swelling.

Spiders that may bite include the yellow sac spider (Cheiracanthium inclusum), the parson spider (Herpyllus ecclesiasticus) and the grass spider (Agelenopsis pennsylvanica).

The yellow sac spider is light-colored and has a body length of less than 1/2 inch; it's a nocturnal hunter, and it hides in woodpiles and other secluded locations during the day.

The parson spider is a swift-moving hunting spider that hides under rocks and in woodpiles. It is about 1/2 inch in body length and dark-colored with pale markings.

The grass spider is larger; a female can attain a body length of up to 8/10 inch and a male 7/10 inch; both genders have long legs. A grass spider is medium brown with darker stripes on its back. It builds a funnel-shaped web in low-growing foliage then lurks inside the funnel as it waits for prey to enter the web.

If you think you were bitten by a widow spider or a recluse spider, then seek attention from a doctor or an emergency room right away. In most cases, physicians will recommend that you use ice to treat swelling from the bite and take an over-the-counter pain reliever to treat pain. They will also likely advise you to seek further medical attention if you develop a fever, an ulcerated sore or any other sign of infection. In rare, severe cases, treatment of a widow bite with antivenin may be required.