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Can someone identify this brown spider in California

Can someone identify this brown spider in California


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Spider found on transit case from California. Approx 1 1/2 inches leg span. Is it poisionus?


It looks a lot like a Kukulcania hibernalis, or southern house spider. This one appears to be a female and if it were to bite you then it would be painful, but not dangerous. These spiders typically keep to themselves so unless you find one hanging in a really bad place it's better just to leave them alone.

For further information you can look here:

https://spiderid.com/spider/filistatidae/kukulcania/hibernalis/


The Persistent Myth of the California Brown Recluse

As the Southern California interior cools with aching slowness and temperatures threaten to drop into the 90s, desert dwellers start to come out of their long summer slumber and get some work done. For homeowners, gardeners, and anyone else charged with tidying up the brown and wizened late summer landscape, that can mean sticking their arms up to the elbow in dried weeds, wind-blown debris, and dead garden plants. And it's also about this time that those of us who work outdoors hear cautionary tales of the Brown Recluse spiders that lurk in that tall dead grass, and of the tale-teller's friend (or cousin or former co-worker) with a scar on his arm the diameter of a softball from an old brown recluse bite that invariably almost killed him.

It may ruin your enjoyment of those stories to learn that the Brown Recluse spider, Loxosceles reclusa, does not in fact live in California. What's more, even where they do live, they're shy, they can often be handled barehanded without incident, and the vast majority of the bites they eventually decide to inflict go almost unnoticed by their human victims. Almost all of the nasty sores blamed on Brown Recluses are caused by something else. We have nothing to worry about from Brown Recluses in California. At least that's what the debunkers say. But even though those debunkers are correct, the "Brown Recluse in California" situation is slightly more complicated than those baldly stated facts might lead you to believe.

Here's the issue. There are no Brown Recluse spiders in California, at least hardly ever. Maybe six specimens of Loxosceles reclusa have been verified here in the state of California's history. Speaking purely statistically, it is more likely that you will have an affair with a sitting California Governor than that you'll see a Brown Recluse in the Golden State.

Recluses don't move around much. Many spiders can migrate by extending a strand of silk long enough to catch a breeze, then drifting on the wind for long distances. The arachnologists call this method of migration "ballooning," though it's really more like flying a kite than a balloon. Regardless of the terminology, it's an effective -- if somewhat aimless -- way for spider species to expand their range. And recluses can't do it. The only way Brown Recluses will ever get to California is accidental hitchhiking in some Midwesterner's moving boxes. (They seem to like cardboard.)

So: no Brown Recluses in California, practically speaking. You can exhale.

Now inhale again. There are two other species of recluse spider resident in the state: Loxosceles deserta, the Desert Recluse, which lives pretty much where you might expect from the name and northward into the San Joaquin Valley, and Loxosceles laeta, the Chilean Recluse, an import that has gained a foothold -- presumably an easier task with eight feet -- in Los Angeles. Every once in a while a few individuals of the species Loxosceles rufescens, the Mediterranean Recluse, will show up on unloading cargo ships no populations have ever been found in the state. The fun part: these other species of recluse spiders come in a whole rainbow of colors from pale buff to tan to manila to a deep, rich cafe con leche. Only Loxosceles reclusa is properly called the Brown Recluse spider. Those other species aren't Brown Recluse spiders. They're just recluse spiders that happen to be, well, brown.

Yeah, I find it confusing too.

Really, what we have here, when this topic comes up, is yet another example of scientists and non-scientists using the same words, completely reasonably, to mean different things. It's the same phenomenon as we see in those depressing creationist arguments in which evolution, the best-established fact in the life sciences and the phenomenon without which, as biologist Theodosius Dobzhanski put it, nothing in biology would make sense, is described as "only a theory." To the biologist, "theory" is like a fact, only bigger: it's the conceptual framework on which you hang facts so that they suddenly all make better sense as a whole. To the layperson, "theory" means "wild and unsupported guess." Same word, two completely different meanings, both uses right in context, and confusion the result. Likewise with Brown Recluses versus recluses that aren't Brown Recluses in the strict sense but which are, nonetheless, brown. And recluses. The scientists say one thing, the non-scientists say the opposite thing, but they use the same exact words to say those two opposing things. It is of such complexities that a science writer's career consists.

More to the point, though: are the Desert Recluse and the Chilean Recluse as dangerous as the Brown Recluse? In the words of the Integrated Pest Management department at the University of California, Davis:

The UC Davis IPM folks go on to say that:

People live around large concentrations of Brown Recluse Spiders in the Midwestern US and no one panics. Arachnologists handle members of a number of Loxosceles species somewhat casually, as you can see from the photos on this page of a bulletin board run by the Southern California Arachnid, Bug, Invertebrate, Entomological Society (SCABIES). A study published in 2002 cited a family in Kansas that collected 2,055 Brown Recluses from inside their house in a six-month period. At the time of the study, no one in that family of four had ever been bitten by a Brown Recluse. Five years later, according to one survey of the species, the mother of that household was bitten on the finger while doing laundry and the spider was positively identified. Her finger turned red and swelled slightly, and then she recovered.

So what's behind the panic? Unfamiliarity with the species is almost certainly part of the problem. Most Californians live within a few feet of a considerable number of highly venomous Black Widow spiders, and there isn't the same folkloric nervousness about that much more dangerous species. When a spider mostly lives in far-off places like Arkansas, it becomes more mysterious and its danger more alluring, a much better growth medium for urban legends.

And some of the nervousness seems to stem from the willingness of medical professionals to diagnose any necrotic skin lesion of undetermined cause as a "Brown Recluse Bite." According to that UC Davis site,

Other causes of necrotic lesions that are misdiagnosed as Brown Recluse bites include Lyme Disease, Herpes simplex, Herpes zoster (chickenpox or shingles), diabetic ulcers, and -- perhaps most troublingly -- group A Staphylococcus infections, which include methicillin-resistant Staphylococcus aureus (MRSA), popularly known as "flesh-eating bacteria." That last ailment can become quickly fatal if massive medical intervention is delayed for any reason -- including misdiagnosis as a spider bite.

All that said, there's still the off chance that you might find a Desert Recluse in the desert, and you might as well avoid an unpleasant interaction. They don't generally like non-native, irrigated plantings, but if you have a more naturalistic landscape setting, you might be providing them with the kind of habitat they like: under pieces of bark, in leaf litter, and detritus. They are reputed to be especially fond of desert woodrat dens. Move firewood and brush away from the foundation of your house, store your garden gloves and workboots in a sealed plastic garbage bag rather than out in the yard, and shake any such item of clothing out before putting it on, and you should be able to avoid becoming California's first completely authenticated Recluse Spider bite victim.

Not a Brown Recluse bite, though. Let's just get that part straight right here.


The black widow spider has a nasty reputation, so if you&rsquore a California resident, you should learn how to identify it. You may think female black widow spiders consume the males after they mate, but this hardly ever occurs (although this is where the common name of widow spiders comes from).

In California, you may run into the western black widow spider (latrodectus hesperus). Females are dark in color (they are typically black but can also be dark brown). Males are generally not black and are smaller than the females. Adult western black widow females are 5/16 to 5/8 inches in length. The abdomen of the western black widow female has an hourglass-shaped mark that&rsquos usually red or orange. Western black widows are typically located in shielded, dry spots such as hollow stumps, sheds and barns.

You might be concerned about the black widow spider&rsquos poisonous bite. Know that male black widow spiders hardly ever bite, but females will bite to defend themselves - particularly when they are protecting their eggs. If you are bitten, you may or may not feel a pinprick. The pain typically comes nearly right away, though. You may also experience swelling and redness. High blood pressure, nausea and sweating are possible, among other symptoms. Get medical attention right away if a black widow spider bites you.

Have you seen black widow spiders around your property or do you suspect they&rsquore around? You should reach out to a pest professional as soon as possible. Contact Western Exterminator to fight the problem.


Brown Widow Spider

The Situation: The brown widow spider, Latrodectus geometricus,became established in Southern California in early 2000 and has become well entrenched as part of the local spider fauna in urban Los Angeles and San Diego. The brown widow spider is continuing its expansion in Southern California and could possibly move northward into Central California.

The brown widow is suspected to have evolved in Africa although it was first described from South America, which adds confusion as to where it might have originated. The Brown Widow Spider is a cosmopolitan tropical and subtropical spider having established populations in Hawaii, Florida, some Caribbean Islands, parts of Australia, South Africa, Japan, and Cyprus. In North America, the Brown Widow Spider was restricted for many decades to the Florida peninsula. However, around the year 2000, it started showing up in other Gulf Coast states. Brown widows are now known from Texas to Georgia and South Carolina. As specimens were found in new locations in the southeastern United States, this species was simultaneously being collected with greater frequency in southern California. The first specimens were collected in Torrance in 2003. After that, the spider was found with greater frequency in Los Angeles, Orange and San Diego counties.

Description of the Brown Widow: Unlike its starkly black-and-red colored relative, the black widow, the coloration of a brown widow consists of a mottling of tan and brown with black accent marking. In mature females, there is usually a dorsal longitudinal abdominal stripe and three diagonal stripes on each flank. At the top of each diagonal stripe, there is a black mark, which is rather conspicuous and square-ish. The Brown Widow Spider does have an hourglass but it is typically an orange shade rather than the vivid red of a black widow. The brown widow looks similar to immatures of the western black widow spider, the latter of which has smaller black spots on the top of the diagonal abdominal stripes and more olive grey background coloration. Being able to discern brown widows from immature black widows is therefore difficult and requires some experience. However, a more diagnostic feature of a brown widow is its egg sac. Most spider egg sacs that are free (i.e., are not attached to flat surfaces) look like a lemon drop candy or a little cotton ball with indistinct edges. The egg sac of a brown widow has multiple silk spicules projecting out from the surface. The egg sac has been described as looking like a large pollen grain or a World War II harbor mine designed to blow up ships. The egg sac of the Brown Widow Spider is so distinctive that it is readily recognizable.

Reproduction: Brown widows are prolific breeders in that they can produce many egg sacs in a lifetime, often several in quick sequence. They lay about 120-150 eggs per sac and can make 20 egg sacs over a lifetime. In comparison, the larger western black widow spiders lay about 300 eggs per sac but make 10 or so egg sacs before they die.

Habitat Preferences: The brown widow builds its web in secluded, protected sites around homes and in woody vegetation with branches. Some typical sites selected by brown widows for web building are empty containers such as buckets and nursery pots, mail boxes, entry way corners, under eaves, storage closets and garages, recessed hand grips of plastic garbage cans, undercarriages of motor vehicles that are stationary for long periods, and the undersides of outdoor furniture and wrought iron railings. They choose places that are more exposed than sites chosen by black widows and hence, appear to be at higher risk for interactions with humans as for as bites are concerned.

Spider Bites: The bite of a brown widow spider is minor in comparison to that of a black widow. Although one frequently cited study demonstrates that, drop per drop, brown widow spider venom is as toxic as other widow species, venom toxicity is only one aspect when considering a spider's bite potential. An African study with 15 verified bites demonstrated that the brown widow spider bite victims showed none of the classic symptoms of latrodectism, a response induced by neurotoxins in the venom of spiders in the genus Latrodectus (e.g., brown widows, black widows [L. mactans], Australian redbacks [L. hasselti], European black widow [L. tredecimguttatus], and New Zealand's katipo spider [L. katipo]). The reason for the weaker effect of brown widow bites on humans is possibly because the brown widow does not have or cannot inject as much venom as its larger relatives. The two major symptoms of a brown widow bite were that the bite hurt when it was inflicted and it left a red mark. These two symptoms are not much different from the bite of normal household spiders. However, there is one recent report of a verified brown widow bite manifesting in more severe symptoms that required hospitalization of the bite victim.

Brown widows appear to be occupying the same niche as black widows so therefore, there may be a shift in the species composition. Considering that the brown widow is less dangerous and may be supplanting the native western black widow from habitats, it is conceivable that the risk of serious injury from overall spider bite may decrease in southern California as the brown widow spreads.


Brown Recluse Bite Symptoms

Most brown recluse bites either don't have any symptoms at all or there is a little swelling with a red bump. Some bites will develop a boil or a pimple. These may be completely indistinguishable from an ingrown hair or a skin infection like staphylococcus or streptococcus.

One extensive review of spider bites notes that tissue death around the bite location can spread within a few days. You might notice skin that is red near the center or boil, turning white, then blue as it spreads.  

Some of the worst brown recluse bites can lead to necrotic arachnidism, which looks like an open wound that doctors often call ulcers. The term necrotic arachnidism literally means tissue death by means of a spider bite.  

Skin infections can lead to necrotic ulcers which look similar to those caused by brown recluse bites. The difference is that necrotic skin infections can be much more dangerous and treatment with antibiotics is possible, so it's very important you see a doctor.

There are very few confirmed deaths from loxoscelism. A 2017 study looked at loxoscelism cases ranging from 1995 through 2005. Of the 57 reported cases of moderate to severe loxoscelism, only two resulted in death. Both individuals—an older man and a young girl—were healthy prior to the bite.  

It should also be noted that the study found 373 possible cases of loxoscelism over that 20 year period. The majority resulted in only minor symptoms that cleared up within a few weeks.


Sac Spiders

Sac spiders are typically found outdoors, but some species, including the yellow sac spider (Cheiracanthium mildei), often wander into homes when the weather is cool or when a plentiful supply of small insects is indoors. Sac spiders are hunting spiders that don't build webs but instead roam at night in search of prey during the day, they stay away from activity and may lurk high on walls or ceilings. They are small, usually about 1/4 inch in body length, and are pale tan, yellow or green.

Sac spider venom includes a cytotoxin that can cause a reaction similar to, but typically less severe than, that of a recluse spider bite. The sac spider bite is usually immediately painful, and sometimes a blister and slow-healing sore will develop at the site of the bite. Reactions to sac spider bites are generally not significant except in individuals who are especially sensitive to the venom.


Dr. Cameron Jones Recounts His Work as a Behavioral Ecologist

/>Cameron Jones poses with his study system (widow spiders, genus Latrodectus). Photo courtesy of Cameron Jones.

Content Editor: Alexia Williams

Hidden among the aquariums and aviaries at the Center for Aquatic Biology and Aquaculture lies a room full of black widow spiders. Far from an arachnophobe, this lab is where Cameron Jones, a recent Ph.D. graduate in the Animal Behavior Graduate Group (ABGG), carried out his experiments on behavioral syndromes (also known as “animal personality”). Jones’ research, conducted under the guidance of Dr. Andy Sih, centers on how the individual personalities of native and invasive species affect their success in an urban environment.

To do this, Jones studied interactions between the native black widow spider (Latrodectus hesperus) and the invasive brown widow (Latrodectus geometricus), which have begun spreading across southern California. Although many may consider the black widow a dangerous pest, these spiders are a native species under threat from invasives. By studying these spiders both in the field and in the lab, Jones discovered how behavioral types - or personalities - in each species contributed to these interactions. Jones was awarded a prestigious National Science Foundation Graduate Research Fellowship in support of this work in 2016.

A black widow spider. Photo by Graham Montgomery, courtesy of Cameron Jones.

In his dissertation Jones found that in the wild, brown widows appear to avoid black widows, but when they do live near black widows, they build higher web “retreats” and tend to show more aggressive behaviors. This aggression may facilitate invasive avoidance of native species, which ultimately influences the interaction of the two spiders where they overlap. These findings shed light on how variation in individual animals’ behavior can affect a community’s composition, especially relevant in a changing world where species are constantly coming into new contact due to human impacts.

Before starting at UC Davis, Jones was conducting research on huntsman spiders with Dr. Linda Rayor as an undergraduate at Cornell University. However, Jones had been studying spiders and insects long before joining Rayor’s lab. While growing up in Vallejo, Jones’ entomological interests were encouraged by his uncle (who also doubled as his field assistant during research). Returning to Davis brought Jones closer to home, family, and the community of invertebrate species he had been fascinated with as a child.

Jones setting up a mesocosm for animal behavior research at the Center for Aquatic
Biology and Aquaculture. Photo courtesy of Cameron Jones, taken by A. Munson.

To conduct his independent research, Jones established his own field sites across urban areas in California, ranging from Riverside to Davis. He assessed web types, species distributions and abundances, and collected individuals to observe in the lab. This involved searching for webs in the evenings - when spiders are most active - in eaves, tunnels, and even among the undercarriages of long-parked cars. However, Jones' field work was made more dangerous solely because of the color of his skin. “I would first always go to the local [police department] and record my [conversation] with them when doing urban ecology,” Jones shared on Twitter, “Not because it would save my life… but maybe my family would have some sort of evidence should something tragic happen. This is our reality of being black in America”.

Despite this, Jones remains hopeful about the potential for progress in academia and beyond. “I really value the support I received from ABGG faculty and students. I felt as though there was a genuine effort to try and make a safe space for minoritized students,” Jones says, “And now, more than ever, I'm seeing both collective outrage at what has been happening for far too long in America and overwhelming support from non-Black Americans that are fighting for change. I encourage that we don't grow weary in this long fight to end systemic injustice and that we continue to uplift and listen to one another.”

To learn more about how to combat and eliminate systemic, institutionalized racism, please visit UC Davis' Resources for Racial Trauma, created by the UC Davis Office of Diversity, Equity, and Inclusion.


Brown Recluse Spider

Many types of spiders live around homes and buildings. Most are harmless, and many are beneficial given they prey upon other nuisance insects, like mosquitos or flies.

One spider found in Kentucky and much of the Midwest that is potentially dangerous is the brown recluse. It is sometimes referred to as the ‘violin’ or ‘fiddleback’ spider because of the violin-shaped marking on its dorsum. Although brown recluse spider bites are rare, the venom can sometimes cause serious wounds and infestations should be taken seriously.

Fig. 1: Brown recluse spiders often have a fiddle-shaped marking.

Distribution and Diagnosis

The brown recluse spider, Loxosceles reclusa, is found throughout the south central and Midwestern United States. Infestations in Kentucky are more common as one travels westward. Other species of Loxosceles spiders occur in the southwestern U.S. and southern California, but the brown recluse is the most notable and widespread. Recluse spiders are rare outside their native range. In general, these spiders are widely over-reported and less common than perceived. Occasionally, one or a few spiders may be transported to a non-native area in boxes or furnishings, but infestations seldom become established.

Fig. 2: Distribution of the brown recluse spider (dark shading) and other species of Loxosceles spiders in the U.S. (light shading) (adapted from distribution map of R. Vetter, Univ. Calif. Riverside).

Though variable in size, adult brown recluse spiders with legs extended are about the size of a U.S. quarter. Coloration ranges from tan to dark brown, and the abdomen and legs are uniformly- colored with no stripes, bands or mottling. The legs are long and thin and lack conspicuous spines. For laypersons, the most distinguishing feature of a brown recluse is a dark violin-shaped mark on its back, with the neck of the violin pointing toward the rear (abdomen) of the spider. This feature is consistent in adult brown recluses, but sometimes less obvious in younger spiders.

Fig. 3: The banding on the legs of this wolf spider is one indication that it is not a brown recluse.

A more definitive diagnostic feature is the eye pattern -- brown recluses have a semi-circular arrangement of six eyes (three groups of two) while most other spiders have 8 eyes. Seeing this feature requires a good quality hand lens. Many harmless brown spiders are mistaken for the brown recluse, so it is prudent to have specimens confirmed by an entomologist or knowledgeable pest control firm.

Fig. 4: Brown recluse spiders have three pairs of eyes, arranged in a semi-circle.

Habits and Development

In nature, brown recluse spiders live outdoors under rocks, logs, woodpiles and debris. The spider is also well adapted to living indoors with humans. They are resilient enough to withstand winters in unheated basements and stifling summer temperatures in attics, persisting many months without food or water. The brown recluse hunts at night seeking insect prey, either alive or dead. It does not employ a web to capture food — suspended webs strung along walls, corners, ceilings, outdoor vegetation, and in other exposed areas are almost always associated with other types of spiders. In homes, such webs are often produced by harmless cobweb or cellar spiders. While sometimes considered a nuisance, spiders like the cobweb or cellar varieties prey upon other pests (including brown recluses), and in this sense could be considered beneficial.

Fig. 5: Cobweb spiders (left) and cellar spiders (right) often build webs in homes, but are harmless.

During daylight hours, brown recluse spiders typically retreat to dark, secluded areas. They often line their daytime retreats with irregular webbing, which is used to form their egg sacs. Adult female recluses seldom venture far from their retreat, whereas males and older juveniles are more mobile and tend to travel farther. Consequently, they are more likely to wander into shoes, clothing or bedding at night and bite people when they inadvertently become trapped against the skin. At times, brown recluse spiders will be seen during daylight hours crawling on floors, walls and other exposed surfaces. Such behavior can be triggered by hunger, overcrowding, pesticide application, or other factors.

About 40-50 eggs are contained within 1/3-inch diameter off-white silken egg sacs. The tiny emerged spiders gradually increase in size, molting five to eight times before becoming adults. The molted (shed) skins of the brown recluse have a distinct outstretched appearance and can be useful in confirming infestation.

Fig. 6: Shed skins of a brown recluse spider

Brown recluse spiders mature in about a year and have an average lifespan of 2 to 4 years. The females produce up to 5 egg sacs in a lifetime. Infestation levels in homes vary greatly, ranging from one or a few spiders to several hundred.

Bites and Medical Significance

Like other spiders, the brown recluse is not aggressive. It is quite common, in fact, to live in a building that is heavily infested and never be bitten. Most bites occur in response to body pressure, when a spider is inadvertently trapped against bare skin. Some people are bitten when they roll over a brown recluse in bed. Other bites occur while moving stored items or putting on a piece of clothing that a spider has chosen for its daytime retreat. Brown recluse spiders have very small fangs and cannot bite through clothing.

The initial bite is usually painless. Oftentimes the victim is unaware until 3 to 8 hours later when the bite site may become red, swollen, and tender. The majority of brown recluse spider bites remain localized, healing within 3 weeks without serious complication or medical intervention.

In other cases, the victim may develop a necrotic lesion, appearing as a dry, sinking bluish patch with irregular edges, a pale center and peripheral redness. Often there is a central blister. As the venom continues to destroy tissue, the wound may expand up to several inches over a period of days or weeks. The necrotic ulcer can persist for several months, leaving a deep scar.

Infrequently, bites in the early stages produce systemic reactions accompanied by fever, chills, dizziness, rash or vomiting. Severe reactions to the venom are more common in children, the elderly, and patients in poor health. Persons bitten by a brown recluse spider should apply ice, elevate the affected area, and seek medical attention immediately.

Medical Misdiagnosis

Spider bites are difficult to diagnose, even by physicians. Contrary to popular belief, it is difficult to diagnosis a brown recluse spider bite from the wound alone. Many medical conditions mimic the necrotic-looking sore from a recluse bite, including bacterial and fungal infections, diabetic and pressure ulcers, and gangrene. Several misdiagnoses have arisen from outbreaks of drug-resistant infections by Staphyloccus aureus (commonly referred to as a Staph infection). That bacterium produces painful skin lesions that resemble recluse bites, and can run rampant in close living quarters such as hospitals, camps, barracks, and correctional facilities. Similar-looking lesions can also be caused by other types of insects and arthropods.

Fig. 7: Many medical conditions are mistaken for brown recluse bites. The wound on the left is from a recluse spider, the one on the right from a bacterial infection.

Suspected bites occurring outside the native range of the brown recluse spider are particularly unlikely, given that surveys rarely yield recluses in non-native areas. Presumptive bites become even more unlikely if thorough inspection of the premises yields no sign of brown recluse spiders. If possible, anyone bitten by what is thought to be a brown recluse should try to collect the specimen and bring it to a qualified individual for identification. Even crushed or damaged specimens can usually be identified. Confirmation by an expert will help the physician decide on the appropriate course of treatment.

Controlling Infestations

Brown recluse spiders are difficult to eradicate, largely because of their secretive habits. Virtually any dark, undisturbed area can serve as harborage, and many such places occur within buildings. Because of this (and the potential health threat), treatment is best performed by professionals.

Where They Hide –Thorough inspection with a bright flashlight is needed to reveal the location and extent of infestation. Likely hiding places include crevices, corners, and wall-floor junctures, especially behind clutter and stored items. Reducing clutter affords fewer places for the spiders to hide and can enhance effectiveness of treatments. Brown recluse spiders may also live behind walls, and inhabit the voids within concrete block foundations. In infested garages, attics, basements and crawl spaces, the spiders, egg sacs, and distinctive shed skins are often found along joists, sills and rafters, as well as under rolled insulation. In living areas, they sometimes inhabit crevices behind and beneath beds and furniture, closets, clothing, shoes, and stored items. When sorting through boxes or materials, wear long sleeves and gloves to avoid being bitten. Brown recluse spiders also live above suspended ceilings, behind baseboards and woodwork, and within ducts and registers.

Fig. 8: Thorough inspections are needed to detect and treat hidden infestations.

Outdoors the spiders may be found in barns, sheds, woodpiles, and under anything laying on the ground. They also commonly reside behind shutters. Migration indoors can be reduced by moving firewood, building materials, and debris away from foundations. Sealing cracks and holes in a building's exterior can further help to keep these, and other pests, outdoors. Some of the more common entry points for brown recluse spiders include gaps under doors, vents and utility penetrations, beneath the bottommost edge of siding, and where eaves and soffits meet the sides of buildings. Outdoor populations of brown recluse spiders are less common in the northern portions of its range.

Use of Glue Traps –An excellent way to survey for brown recluse is to install flat, sticky cards known as glue traps. Often used to capture mice and cockroaches, the traps can be purchased online or at grocery, hardware or farm supply stores. The best glue traps for capturing the spiders are flat, like thin pieces of sticky cardboard without a raised perimeter edge.

Fig. 9: Brown recluse spiders caught on a glue trap. Several traps should be placed into corners and flush along walls.

The more glue traps used the better — dozens placed throughout a home will reveal areas where spiders are most abundant. Traps should be placed in corners and along baseboards and 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 into places where people are accidentally bitten. Ongoing eradication efforts can be judged by the number of new spiders caught in traps. Glue traps should be installed before applying insecticides since some products will cause spiders to become active and wander into traps.

Use of Insecticides –Brown recluse spider elimination will often require use of insecticides. Some spiders will not be caught in glue traps, especially the adult females, which stay hidden more so than male spiders. Insecticides should be applied into cracks and other areas where spiders are likely to be hiding, attempting to contact directly as many as possible. Liquid, aerosol, and dust formulations may be employed.

Fig. 10: Insecticides are often needed to control infestations.

Dust insecticides are particularly effective for treating cracks along baseboards, sills, joists and rafters in basements, crawl spaces, and attics. Dusts also work well when treating under insulation, within voids of concrete block foundations, and behind light switch and outlet plates to contact spiders traveling along wires from attics. Effective dust insecticides include Cimexa®, Drione® and Tri-Die® (silica gel), Tempo® (cyfluthrin), and DeltaDust® (deltamethrin). Apply the dust as a fine deposit barely visible to the naked eye. Spiders and other pests tend to avoid powdery accumulations much as we would avoid walking through a snowdrift. The easiest way to apply such a small amount is with a ‘bellows’ hand duster sold in hardware stores or online.

Fig. 11: Dust formulations are easier to apply with a bellows duster.

Insecticides can also be sprayed into harborages and places where spiders tend to travel. Effective ingredients (e.g., cyfluthrin, bifenthrin, deltamethrin, lambda cyhalothrin) are often found in products used to control cockroaches, ants, and other crawling insects. The sprays can also be applied outdoors (behind shutters, the bottommost edge of siding, along foundations, etc. Total-release pesticide foggers known as ‘bug bombs’ are seldom effective against these spiders, and should only be considered when treating otherwise inaccessible areas.

Avoiding Bites

As control measures are being implemented, precautions can be taken to further reduce the chance of being bitten. Beds should be moved away from walls, and remove any bed skirts/dust ruffles to break contact with the floor. Shoes and clothing should also be kept off floors, or at least shaken out before wearing. Remove excess clutter and store seldom used items in plastic storage containers. There may be some comfort in knowing that bites are a rare occurrence, even in dwellings where brown recluses are abundant.

CAUTION: The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication. ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE.

Please note that all photos in this publication are copyrighted material and may not be copied or downloaded without permission of the author.


Brown recluse bite

The brown recluse has a venomous bite, and anyone bitten should seek immediate emergency medical help, according to the National Institutes of Health.

Like most spiders, the brown recluse typically only bites when disturbed &mdash though it is possible to inadvertently threaten them. The Texas A&M AgriLife Extension Program reports that this may happen if a spider is caught in bedding or clothing.

"People react differently to bites," Bills said. According to The Integrated Pest Management Program at UC Berkeley, 90 percent of bites heal without medical attention or scarring. Reactions to a brown recluse bite vary depending on the amount of venom injected and the individual&rsquos sensitivity levels, reports The Ohio State University. Some people may experience a delayed reaction, others an immediate reaction, and others no reaction at all. Many brown recluse bites leave a small red mark that heals quickly, and the vast majority of bites do not leave scars.

For those with higher sensitivity levels, a small white blister appears at the bite site soon after the bite. The tissue may become hard. Lesions are dry, blue-gray or blue-white patches with ragged edges surrounded by redness. This color pattern has yielded the nickname "red, white and blue," and, in severe reactions, the bite site can develop a "volcano lesion," according to The Ohio State University. The damaged tissue becomes gangrenous and leaves an open wound that can be as large as a human hand. It can take eight weeks or longer for full recovery, and scars may result.

According to the NIH, symptoms of a brown recluse bite may include itching, chills, fever, nausea, sweating and a general feeling of discomfort or sickness.


  • You have a fever or chills.
  • The skin around your wound gets red, or the wound gets more painful.
  • You have a headache, or nausea and vomiting.
  • You have numbness or tingling in the bite area.
  • You have trouble talking, walking, or breathing.
  • Your urine is darker, or you urinate less than is usual for you.
  • Your wound does not stop bleeding even after you apply pressure.
  • Your wound or bandage has pus or a bad smell.

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