Unlike many types of spiders in our homes, sheds, and garages, brown recluse spiders are not harmless. Indeed, they are beneficial, to an extent, as acting as insect and pest control. However, their bites can cause severe medical reactions.
And a word about using the so-called “fiddle back” or “violin” marking on the brown recluse spider’s dorsum; I’ve never seen it, not in close-ups or in person.
I think it would be better described as a wine glass with a long stem and small base—with the cup pouring the wine on top of the spider’s head. Either way, too many species of spider have such markings. Fortunately, there is a more straightforward way to identify brown recluse spiders.
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Positively identifying brown recluse spiders.
Identifying brown recluse spiders begins by considering where you have found the spider in question.
Brown recluse spiders (Loxosceles reclusa) are commonly found in the Southern Central and Midwestern states. Sure, you could be looking at a traveler who has hitched a ride north, further east, or west. However, that spider is well outside its native territory. Indeed, it will never procreate enough to become an actual problem on the level of an infestation.
Traveling spiders (like the Hobo spider) sometimes enter and inhabit new regions. But the brown recluse spider won’t survive such migrations.
So, unless you have moved from western Kentucky to, let’s say, New York, you should be okay. However, there’s no sense in taking chances. Perhaps be careful when unpacking those boxes and chairs—just to be sure. Heck, the E.R. doctor in New York might be untrained to recognize your bite symptoms.
Brown recluse spiders: The eyes have it!
Adult brown recluse spiders are about the size of an American quarter (nearly an inch). Surprisingly, they are brown or tannish in color. Their abdomens and legs have no bands, mottling, stripes, or visible spines.
Don’t forget that they neither play violins or fiddles nor possess images of such musical instruments in markings or tattoos.
What sets the brown recluse spider apart from most other spiders you will encounter? First, they only have six eyes!
Retake a look at the close-up photo above. You’ll see that brown recluse spiders have a semi-circular eye arrangement (three sets of two), but most spiders have eight eyes.
Okay, I’ll admit that counting the number of tiny eyes on an inch-long spider is difficult. And no one has a magnifying glass at home, which is readily available anymore. So grab that iPhone, snap a photo, and zoom in on the spider’s face.
When you get to the hospital, you can use the picture to help diagnose why you are shrieking in agony and convulsing on their table. Just kidding, we’ll talk more about the bite of brown recluse spiders later.
The slanting legs of the brown recluse spider.
Brown recluse spiders are rather plain with uniformly tan or brown abdomens, but their legs (which lack spines, as noted above) are covered in fine hairs. In addition, these legs are slanted (hence the scientific name Loxosceles meaning, well, slanted legs in Latin).
Brown recluse soldiers do not walk funny; instead, the rest with their legs slanted.
The taxonomy of brown recluse spiders.
As found in the Integrated Taxonomic Information System (ITIS), the taxonomy of brown recluse spidersis:
- Kingdom: Animalia
- Subkingdom: Bilateria
- Infrakingdom: Protostomia
- Superphylum: Ecdysozoa
- Phylum: Arthropoda
- Subphylum: Chelicerata
- Class: Euchelicerata
- Subclass: Arachnida
- Order: Araneae
- Family: Sicariidae
- Genus & species: Loxosceles reclusa
Why are they called brown recluse spiders?
Brown recluse spiders are like reclusive people. They will go out of their way to avoid any interaction with humans. Let’s just say they are shy. They hunt and build their webs in the secretiveness of the dark.
How brown recluse spider captures their prey.
By sunrise, brown recluse spiders have filed back to their “retreat” in any number of crevices and cracks they find in the wild or your home. Here they will wait for dusk before resuming most of their activities.
Sadly, brown recluse spiders find such excellent habitats in your house that they are called “house spiders.”
The bite and symptoms of brown recluse spiders.
You must stick your hand in a brown recluse spider web or seriously disturb one to receive a bite.
However, accidents do happen. For example, if a brown recluse spider bites you, you can expect the pain to range from mild to severe after a few hours.
Less than 10% of bites from brown recluse spiders cause any real tissue damage (there is no anti-venom available yet), but most bites heal and do not leave scars—even if medical attention is not sought.
Of course, everyone reacts differently to spider bites, so treat with first aid, collect the spider if possible, and seek immediate medical attention.
Brown recluse spiders: Abundance, mating ,and reproduction.
Brown recluse spider can live in the wild (and your home) for nearly four years. This isn’t always the case, however, as noted in Survival, abundance, and movement of a synanthropic population of the brown recluse spider, Loxosceles reclusa(Araneae: Sicariidae).
“We conducted a two-year mark-recapture study of a synanthropic population of the brown recluse spider Loxosceles reclusa Gertsch & Mulaik, 1940 in northwestern Illinois.
We used joint live encounter and dead recovery models to estimate adult survival, recapture, and dead recovery probabilities. To estimate adult abundance, we used full-likelihood closed-population models. Monthly survival was constant between sexes (0.73, 95% CI = 0.66–0.78), but males were less likely to be recaptured and an additive effect of time revealed highest recapture probabilities in September.
The probability of recovering a marked adult that died during the study was 0.13 (95% CI = 0.07–0.24). Average life expectancy for adults was 94 days, much lower than in prior laboratory studies. Causes of observed mortality were predation by conspecifics and cobweb spiders (Parasteatoda tepidariorum (C.L. Koch, 1841)) or undetermined.
A likely source of mortality for this sit-and-wait predator is starvation. Model averaging of full likelihood closed-population models resulted in adult abundance estimates that were similar between males (28, 95% CI = 20–63) and females (28, 95% CI = 26–38).
However, the total population of adults including those hidden in harborage (boxes, furniture, crevices etc.) was undoubtedly much higher. Based on count data, immature spiders were as abundant as adults early in the year, gradually increasing to a peak three times greater by mid-summer.
Male spiders moved longer distances than females and were less likely to exhibit site fidelity. The average tenure of a female at a specific site was nearly 8 days.
Misdiagnosing brown recluse spider bites.
While there is no effective commercial antivenom approved for use in the United States, brown recluse spiders get a lot of blame and bad press from wounds that resemble their bites. As found in: Medical Myths:
“Physicians in nonendemic brown recluse regions (figure 2) should be cautious in implicating brown recluses in idiopathic necrotic wounds. The medical community needs to be aware of the many causes of necrotic wounds that can be misdiagnosed as recluse bites. Culture of specimens taken from wounds might accurately determine the plethora of causative agents of so-called brown recluse bites, which can vary from being arthropod, bacterial, viral, or fungal in nature or due to underlying disease states.
Conditions that can cause necrotic wounds and/or that have been misdiagnosed as brown recluse bites
- Infections with Staphylococcus or Streptococcus species
- Herpes simplex
- Herpes zoster
- Erythema multiforme
- Diabetic ulcer
- Lyme disease
- Fungal infection
- Pyoderma gangrenosum
- Lymphomatoid papulosis
- Chemical burn
- Poison ivy/oak dermatitis
- Squamous cell carcinoma
- Localized vasculitis
- Syphilitic chancre.”
Treatment of brown recluse spider bites remains controversial.
Background: Treatment of brown recluse spider bites remains controversial; there are multiple options but little evidence of their effectiveness.
Methods: Over a 5-year period, family physicians enrolled consecutive patients with suspected brown recluse spider bites. Usual care was provided based on physician preferences. Topical nitroglycerine patches and vitamin C tablets were provided at no cost for those who wished to use them. Baseline data were collected, and patients were followed-up weekly until healing occurred.
Outcome measures included time to healing and occurrence of scarring. Regression methods were used to evaluate the impact of the 4 main treatment approaches (corticosteroids, dapsone, topical nitroglycerine, and high- dose vitamin C) after controlling for bite severity and other predictors.
Results: Two hundred and sixty-two patients were enrolled; outcomes were available for 189. The median healing time was 17 days. Only 21% had permanent scarring. One hundred seventy-four re- ceived a single treatment modality.
Among this group, 12 different modalities were used. After controlling for other variables, predictors of more rapid healing included lower severity level, less erythema, and less necrosis at time of presentation, younger age, no diabetes, and earlier medical attention.
Systemic corticosteroids and dapsone were associated with slower healing. Predictors of scarring were higher severity, presence of necrosis, and diabetes. Dapsone was associated with an increased probability of scarring.
Conclusions: We found no evidence that commonly used treatment approaches reduced healing time or the likelihood of scarring in suspected brown recluse spider bites. (J Am Board Fam Pract 2004;17: 347–52.)
Preventing brown recluse spider bites.
Keeping the brown recluse spider out of your home means limiting the exterior areas around your house that provide suitable web construction. Then, arrange your living space to prevent the brown recluse spider from crawling up from the floor and gaining access to higher elevations, such as bedding and curtains.
Outside your home, begin by locating any cracks or holes the brown recluse spider could build a web inside. You can begin by treating this area and then sealing them up.
Check for access points anywhere pipes or electrical lines enter through your foundations. Make sure window screens have a tight fit and that vents in attics and your foundation are also sealed.
Now consider the ground vegetation around your home. Remove it if possible, or begin regular treatments to kill the brown recluse spiders who may have established their funnel webs in them.
Eliminating recluse spiders from your home.
Inside your home, the goal is to keep the spider on the floor. If you do this, it will not remain indoors or, at the very least, be unable to build a web and survive for any length of time. A side benefit to keeping the brown spider on the ground is it dramatically reduces the potential for human bites.
And if your home is older, check and replace your door sweeps—you always wondered what they were for anyway.
Keep curtains and bedding materials from touching the floor. Store laundry in a basket and keep your clothes off the floor.
If you live where brown recluse spiders are common, check your sheets and blankets before bed. And shake out your boots and clothes before donning them. Since a brown recluse spider can climb your walls, pull your bed away from windows, curtains, and walls.
Spider pages: Learn how to identify and avoid these spiders.
Spider pages: Learn how to identify and avoid these spiders.