Dangerous Biting Spiders Rare in Ohio
Spiders get a bad rap. They are feared much more than is appropriate based on the dangers they pose
to humans. Having said that, out of the 600 to 700 species of spiders in Ohio there are only two types of
spiders that are medically significant here, the black widow and the brown recluse. Both of these spiders
are uncommon to rare in Ohio.
Black widow spiders (genus Lactrodectus) are found primarily in the unglaciated southern areas of Ohio.
There are two species, the northern and the southern black widows. The species are similar and females
are identified by shiny black bodies with orange-red to red spots on their abdomen. They build messy
cobwebs in dry places such as under rock ledges or beneath the eaves of buildings. The female bodies
are 1/4 to 3/8 of an inch long. The males are much smaller, generally 1/8 to 1/4 of an inch long. The
males are not large enough to bite humans.
Black widows in general are shy spiders and only bite humans if they are pinched or seriously
threatened. Poking a female will generally cause her to move away. Should you be bitten you should
seek medical attention promptly, and ideally take the spider with you to verify its identity. The venom of
a black widow is a neurotoxin and can be deadly in rare cases. Most often a bite is painful but there are
no long-term effects. Mortality is low with no verifiable deaths from black widow spider bites in 50
years according to a report published in 2008 in the Journal “Wilderness and Environmental Medicine”.
Brown recluse spiders (Loxosceles reclusa) have seldom been found in Ohio with only 9 spiders having
been collected, all in buildings. There are many reported sightings of this spider, but when the
specimens are submitted to experts for identification the supposed brown recluse spiders almost always
end up being common spiders that are much less dangerous’
Brown recluse spiders share characteristics with many other spiders, so to identify a brown recluse you
need to be sure that the spider has all the characteristics of its species. First, recluse spiders have six
eyes arranged in pairs giving the appearance that they have only three eyes. Second their legs have only
fine hairs, not stout spines as you see on many type of spiders. Third, the abdomen of the spider is
uniform in color. Fourth, the legs are uniform in color without stripes or bands. Fifth the spider body is
about 3/8 of an inch long. If it is longer than ½ inch it is definitely not a recluse. Sixth, the cephalothorax
(the combined head and chest where all the mouthparts and legs are attached) has a marking that
resembles the shape of a violin. This characteristic is shared with other spiders and should not be used
as a deciding factor. Finally, as their name implies, brown recluses build their webs in out-of-the-way
places. If you see a spider in a web out in the open, it is probably not a recluse.
The venom of brown recluse spiders is a protein that damages tissues. Recent research at the University
of Arizona revealed that it is unique among animal venoms because it attacks lipids and thus damages
membranes in a manner not seen elsewhere in the animal kingdom.
Spiders are extremely valuable predators, consuming many insect pests. While we may not want them
living too close to us, they do provide valuable services to humanity and deserve more respect than fear.
A good source on the identification of Ohio’s common spiders is a field guide published by the Ohio
Department of Natural Resource and available as a download from the Ohio Division of Wildlife.
http://wildlife.ohiodnr.gov/portals/wildlife/pdfs/publications/id%20guides/pub5140.pdf
PHOTO: Female black widow (left) and brown recluse spiders. Black widow seen from ventral side;
brown recluse from dorsal. Photos are at different scale. Credits: Black widow by SHenrich 91 and
Licensed under Creative Commons CC BY-SA 3.0. Brown recluse by Centers for Disease Control and
Prevention, Public Health Image Library and in the public domain.