How to Identify and Misidentify a Brown Recluse Spider
Throughout the year people bring in all types of plant-related problems, weeds, insects, or suspicious
looking critters for identification and solutions to Cooperative Extension centers. Many times these folks
need something identified to make sure their product is protected like an insect versus a disease
destroying a crop and how to prevent infestation. We also get to identify dead snakes, spiders, moths,
flies, and other critters. Most identification is free and a County Extension Agent responds within a few
days. Other pests like bed bugs or mold spores need technical identification from the experts, which for
a small price we will send to the appropriate agency
and get a response within 2-3 weeks.
Frequently homeowners bring in brown spiders
thought to be a brown recluse. Many spiders are
mistaken for brown recluse spiders. In North Carolina
it is HIGHLY UNLIKELY that you will find a recluse
spider. It is possible but incredibly unlikely since their
range extends only to the southwestern-most border of
NC.
What does a brown recluse look like?
Brown Recluse (Rick Vetter)
Brown Recluse (Univ of Kentucky)
Brown Recluse: The yellow highlight shows the
"fiddle" or "violin" shape (R. Bessin, 2000)
There are 7 things that typically describe a brown recluse spider. Some other spiders have a few of these
characteristics but not all. If you can learn to identify your spider as NOT a recluse, you can relieve
your worries. You won’t be able to tell what it is but you will at least know that it is not a recluse spider.
1. Brown recluse spiders have 6 eyes arranged in pairs with a space separating
the pairs. Most spiders have 8 eyes in two rows of four. Seeing this feature
clearly requires a good quality hand lens.
2. Brown recluse spiders have a dark violin shape on the cephalothorax (the
portion of the body to which the legs attach). The neck of the violin points
backward toward the abdomen.
3. Brown recluse spiders have uniformly light-colored legs – no stripes, no
bands.
Brown Recluse magnified
to show 6 eyes (Rick
Vetter)
4. Brown recluse spiders have a uniformly-colored abdomen which can vary
from cream to dark brown depending on what it has eaten; however, it will never have two colors of
pigment at the same time.
5. Brown recluse spiders do not have spines on the legs, only fine hairs.
6. Brown recluse spiders make small retreat webs behind objects, never out in the open.
7. Brown recluse spiders bodies are less than half an inch (actual body length is 3/8 of an inch). That
means the body without legs is less than the length of a dime.
Likely hiding places for brown recluse spiders include crevices, corners, and wall-floor junctures
(especially behind clutter and furniture) in garages, basements and living areas. Reducing clutter affords
fewer places for the spiders to hide, and can enhance effectiveness of treatments.
Do a survey with glue board traps - flat, thin pieces of sticky cardboard, without a raised perimeter edge.
Place traps in corners and along wall-floor junctures, especially behind furniture and clutter since
spiders tend to travel in these areas. Besides being useful for detection, glue traps can capture and kill
large numbers of spiders, especially the males, which are more likely to wander.
Brown recluse infestations will usually warrant the use of insecticides. Egg-laying female spiders are
rarely caught in glue traps because they typically stay hidden. Insecticides should be applied into cracks
and voids. Spray, dust and aerosol formulations may be employed. Dust insecticides are particularly
effective for treating cracks, under insulation, within voids of hollow block foundations, and behind light
switch and outlet plates.
"Bug bombs" and total-release foggers are seldom effective against these spiders, and should only be
considered when treating otherwise inaccessible areas. Treatments can also be made outdoors to help
reduce spider entry. Cracks in exterior walls can be treated, and sprays can be applied along the base of
foundations and likely entry points.
To avoid bites move beds away from walls, drapes and other furnishings, and make sure bed skirts or
long bedspreads do not contact the floor. Shoes and clothing should also be kept off floors, or at least
shaken well before wearing. Remove excess clutter and store seldom-used items in plastic storage
containers.
Even if you have a recluse, bites from them are extremely rare. Ninety percent of brown recluse bites are
not medically significant and heal very nicely, often without medical intervention. Treatment for most
brown recluse bites is simple first aid (RICE therapy – Rest, Ice, Compression, Elevation). Many
conditions are misdiagnosed as recluse bites when their cause is something else like infection, bad
reaction to medication, diabetic ulcers, Lyme disease, or other underlying medical conditions.
Common spiders mistaken for brown recluse:
Long-Bodied Cellar Spider
(B. Newton, 2002)
Grass Spider or Funnel Weaver
(B. Newton, 2003)
American House Spider
(R. Bessin, 2000)
Fishing Spider, Dolomedes
tenebrosus (R. Bessin, 2000)
Female dimorphic jumping spider
(B. Newton, 2004)
Wendi Hartup is an area natural resources extension agent for the Forsyth and Stokes County
Cooperative Extension Service.
SOURCES:
Rick Vetter, Staff Research Associate, University of California Riverside Department of Entomology
Lee Townsend and Mike Potter, Extension Entomologist, University of Kentucky College of Agriculture
Blake Newton, University of Kentucky Department of Entomology