Holmes Lawn & Pest Blog

The Brown Recluse

Brown Recluse Appearance

The brown recluse spider is the most dangerous and deadly species of spider in the United States. While brown recluses (L. reclusa) are not native to Utah, the closely related desert recluses (L. deserta) are more commonly found in southern Utah, and reports exist of them venturing to northern parts of the state. These two species are extremely similar in appearance, and their bites are equally potent and dangerous. Being able to properly identify these spiders could be the difference between life and death, or it could at least save you from severe and permanent bodily harm. 

Appearance

deserta and L. reclusa are so similar in appearance that differentiating them with the naked eye is nearly impossible. There are key attributes of both species that can be used to identify either, and any minuscule differences are ultimately immaterial since both species behave in the same manner and pose the same threat to humans.

These recluse spiders typically grow up to ½ an inch, with few reports of them ever growing near a full inch in length. The colors of brown recluses and desert recluses are somewhere between a sandy tan to a darker brown, and desert recluses are often believed to be a slightly lighter shade of brown. The abdominal area can occasionally be grayish, but it will have a uniform color, tiny hairs, and no markings. If markings are seen on a spider’s abdomen, it is likely not a brown or desert recluse.

The cephalothorax and legs of both recluse spiders are a brownish color, with no markings on the legs. A distinctive violin-shaped mark can be found on the cephalothorax of brown recluses. This same mark can be found on desert recluses, but it is not always a reliable indicator because L. deserta does not have to feature this mark, and many other non-recluse spiders can have the same violin-shaped marking.

An attribute that is rather unique to these recluse spiders is the formation of their eyes. L. deserta and L. reclusa, as well as most other recluse spiders, have only six eyes. These six eyes are arranged in three sets of two eyes at the front of the cephalothorax/head area. The two eyes in each set are clustered so closely together that the spiders appear to have only three eyes, with two evenly placed clusters sitting just above the third cluster that is centered slightly lower.

Recluse spiders account for the most common cases of false identification. The false sightings are due to a mixture of fear and a lack of knowledge about the appearance of a recluse. The easiest and safest ways to rule out a desert recluse or brown recluse are by identifying the size and the markings of a spider. If the spider you see is considerably larger than a U.S. quarter or if there are clear patterned markings on the legs or abdomen, you are most likely not dealing with a recluse spider.

Life Cycle And Behavior

As is the case with many spiders, male recluse spiders will attempt to impress the female in order to mate. The males perform a ritualistic dance that involves movements of his abdomen and pedipalps. If dancing fails, male recluse spiders will sometimes bring an offering of food to the female to persuade her. If his advances are accepted, the male deposits his sperm into a small web and uses his pedipalps to insert it into the female’s reproductive opening, similar to many other spiders.

 

After mating, the female will produce several egg sacs, typically between May and July, that each contain about 50 eggs. Egg sacs will be kept hidden under objects that provide adequate darkness and protection. When the eggs hatch, desert and brown recluses will quickly venture off on their own, and they will reach full maturity in about one year. 

 

Both types of recluse spiders live an average of one to two years, and they are capable of living up to three years if conditions are ideal. They are incredibly resilient creatures that can go several months or longer without any food. If desperate, recluse spiders will cannibalize one another.

 

Staying true to their name, these recluse spiders do not enjoy the presence of humans or other animals. Most experts agree that these spiders prefer a natural environment rather than dwelling inside a person’s home, but they can still find their way inside buildings. Tree debris, leaf litter, dense grass, boulders, and other isolated outdoor areas are perfect for recluse spiders. If they do find their way inside your home, they will gravitate towards undisturbed areas that are dark and quiet, such as basements, garages, and attics.

 

Recluse spiders are hunters, and they inject their deadly venom into their victims after pouncing on them. Like most spiders, desert and brown recluse spiders feed mainly on insects and other bugs that they are able to catch. The webbing they produce is used only for their own protection and not to catch prey. As resilient as they are, these recluse spiders will spend the majority of their lives in their nests/webbed structures, and they will usually leave only to hunt or mate.

How Dangerous Are Brown Recluse Spiders?

The good news about dangerous recluse spiders is that they want nothing to do with you! While their venom can be extremely potent, reports of bites are relatively low due to their aversion to humans. Desert and brown recluse spiders want to inhabit the most isolated areas they can find, which is why you are unlikely to find one in your home. If you do encounter one, it will almost certainly attempt to run and hide from you, and it will probably only attack you if it feels a physical touch.

 

Many people live near recluse spiders and never know it. The creatures tend to prefer outdoor environments, and they will have no need to enter your home if they find a suitable place to make their nests outside. If you do spot a recluse spider in your home, extreme caution must be taken, and professional assistance should be considered when it comes to extracting/exterminating them. 



A bite from one of these recluse spiders will not always result in critical injuries, but the possibility is always present. Recluses may not inject venom every time they bite, but effects of a venomous bite can quickly turn into a serious situation. The venom produced by these recluse spiders is capable of causing severe blistering, nausea, muscle pain, deep tissue necrosis, and even death. Though these effects are not the norm after a bite, the possibility of such severe and life-threatening symptoms justifies the fear of L. deserta and L. reclusa. If you believe you have been bitten by one of these spiders, you should immediately seek medical help before symptoms develop.

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