Brown Recluse Spiders in Colorado: Recognition and Spiders of Similar Appearance Fact Sheet No. 5.607 Insect Series|Home and Garden by W.S. Cranshaw* Brown recluse and related recluse spiders Quick Facts (Loxosceles spp., Family Sicariidae) are, by far, the most commonly misidentified spiders • Colorado has many kinds in Colorado. Unfortunately, also greatly of spiders that are brown overdiagnosed are purported spider bites or have patterning that may caused by brown recluse spiders – a situation resemble brown recluse perpetuated by many in the Colorado spiders. medical establishment as well as through self-diagnosis. • The quickest way to positively Colorado hosts a great many kinds identify a recluse spider is to examine the arrangement of of spiders that are brown or have some Figure 1: Brown recluse spider. (Photo courtesy of patterning that may superficially resemble the University of Nebraska.) the eyes – there should be brown recluse spiders. However, close three pairs. examination can readily distinguish them (see Table 1). • Brown recluse spiders usually have a “violin pattern” on the cephalothorax. Identification • Funnel weaver spiders and The quickest way to positively identify if a spider might be a recluse spider is to examine wood louse hunters are the the arrangement of the eyes. This requires two groups most commonly some magnification. Recluse spiders have mistaken for recluse spiders. three pairs of eyes, a very unusual feature among spiders. Overwhelmingly, most spiders found in Colorado have four pairs. The arrangement of the eyes on the recluse Figure 2: Brown recluse spider. (Photo courtesy of spiders is one pair in the front, the other two Lisa Ames.) along the sides, forming a semicircle. Overall body color is brown, which may range from a light to dark brown. The abdomen is uniformly colored, without patterning. On the cephalothorax (the body region including the head and legs) a brown marking is usually present. This is typically described as a “violin pattern” and the eyes are incorporated into the base of it. The contrast intensity of this pattern can vary among the different recluse species and life stages. (Brown patterning on the cephalothorax also occurs in many Colorado Figure 3. Brown recluse spider showing the violin spiders, including funnel weavers and pattern on the cephalothorax. (Photo courtesy of cellar spiders.) Lisa Ames.) ©Colorado State University Legs of recluse spiders are long and Extension. 2/08. Revised 12/12. thin. The legs have a silky appearance, covered with fine hairs and large spines are www.ext.colostate.edu not present. The legs are uniform in color, *W. Cranshaw, Colorado State University Extension never banded. entomology specialist, and professor, bioagricultural sciences and pest management. 12/2012 Table 1. Features to identify recluse (brown) spiders (Loxosceles species). Eyes 3 pairs, of approximate equal size, arranged in semicircular pattern. Cephalothorax Overall color uniformly brown; Darker brown pattern in center, somewhat resembling a violin, usually present. Abdomen Overall color uniformly brown, without any patterning. Legs Uniformly colored, without any banding or patterning; Silky appearance due to fine hairs; no spines present. Activity Active at night; restricted to web-lined refugia during day. Webs Webs are not produced in open areas where they are readily seen.

Recluse spiders are active at night. known of the recluse spiders found in the Figure 5: Female funnel weaver spider, During the day they hide in dark crevices U.S. is the brown recluse, Loxosceles reclusa. Agelenopsis sp. and hollows. In areas of the U.S. where It occurs in many of the midwestern they are common, recluse spiders found in and south central states, and can be very homes are often found in basements. common in and around homes in eastern Kansas, Missouri, Arkansas, Louisiana, Oklahoma, parts of Texas, and some other Recluse Spiders states. Occasionally it is transported out of in the United States its normal range, but it rarely survives and There are 10 native recluse spiders establishes outside the area. (Loxosceles spp.) in the U.S. with most Most, if not all, of the recluse spiders confined to areas of southwestern states have venom that can cause tissue death bordering Mexico. In addition, the (cytotoxins). Nine protein fractions Mediterranean recluse, Loxosceles rufescens, have been identified in the venom with is occasionally introduced and likely now most attention given to the enzyme Figure 6: Male funnel weaver spider, Agelenopsis sp. established in many parts of the country, sphingomyelinase D, considered the main although nowhere is it considered to be contributor to cell injuries resulting from common. The South American speciesL. bites by these spiders. laeta is established in a few localized areas The amount of venom introduced on both coasts. during a bite, and possibly the toxicity Identification of the variousLoxosceles of the venom, varies among the recluse to the species level can only be done by spiders. For example, the medical an expert. Specimens of Loxosceles that importance of the brown recluse is well are collected from Colorado currently can documented in the literature. However, be identified by personnel at the Denver it has been suggested that bites of the Museum of Nature and Science. The best common South American species,

Figure 7: Cellar spider, side view.

Figure 8: Cellar spider. (Photo courtesy of the University of Nebraska.)

Figure 4: General distribution of Loxosceles spiders in the United States. (Created by Rick Vetter.) and sensitivity to touch. This can further strain can result in lesions similar to those expand exposing underlying tissues as caused by bites of Loxosceles reclusa. the dead cells slough away. This ulcerated area is dry, since capillaries are sealed by the effects of the venom, but it may take a Colorado Arachnids couple of months to heal with permanent Mistaken for Brown scarring sometimes produced. Recluse Spiders Several spiders found in Colorado – and Recluse Spiders some other arachnids – are commonly in Colorado mistaken for brown recluse. These include the following: The brown recluse, and all other recluse Funnel weavers (Agelenidae). The Figure 9: Dysdera crocata, the ‘roly-poly hunter. spiders, are extremely rare in Colorado. funnel weavers are an extremely common, Confirmed specimens at the Denver brown-colored spiders. They get their Museum of Nature and Science collection name from the web they produce, which include only one specimen of Loxoceles is densely constructed of silk to produce a reclusa collected from the state (Boulder mat with a funnel-like retreat area where County, 1996). Also on record are four the spider normally rests. These webs can specimens of the Mediterranean recluse, L. rufescens (Denver, Bent, and Las Animas counties plus one from Larimer County Table 2. Medical conditions with symptoms located at the Colorado State University sometimes confused with brown recluse collection) and a single collection of L. spider bites (adapted from Vetter 2000). apachea (Larimer County). Bacterial Clearly incidence of these spiders • Methicillin-resistant Staphylococcus Figure 10: Running crab spider, Philodromus sp. aureus (MRSA or false spider bite diagnosis) in Colorado is incidental, resulting • Other Staphylococcus infections from occasional transfers coming from • Streptococcus infection L. laeta, are potentially even more chronically infested areas of the country. • Gonococcal arthritis dermatitis • Cutaneous anthrax dangerous. Conversely, only very few Establishment and sustained breeding of Reaction to drugs cases of complications are reported from these spiders in Colorado is much rarer, if it • Warfarin poisoning the ubiquitous Mediterranean recluse occurs at all. (There are two fairly credible Viral (L. rufuscens) and the native southern reports of some species of Loxosceles • Infected herpes simplex California species, L. deserta, suggesting established in a basement area; one each • Chronic herpes simplex • Varicella zoster (shingles) that these are less important medically. in Pueblo and Prowers counties. The Arthropod-induced The remaining species of nativeLoxosceles species involved have not been recorded • Lyme disease species that occur in North America do and the infestations were isolated to a • Rocky Mountain spotted fever not appear to be associated with serious single building.) • Ornithodoros coriaceus bite (soft tick) • Insect bites (flea, mite, biting fly) medical problems. Despite the near total lack of Loxosceles Fungal spp. spiders in Colorado, dermonecrotic • Sporotrichosis Symptoms of Brown lesions are commonly diagnosed • Keratin cell mediated response to fungus (misdiagnosed) as spider bites and, more Topical Recluse Bite specifically, as resulting from the bites of • Poison ivy/poison oak • Chemical burn Brown recluse bites initially may be felt recluse spiders. Other, more likely, causes Lymphoproliferative disorders as a slight pinprick – or not noticed at all. for such dermonecrotic lesions, and causes • Lymphoma The majority of bites result in no further that have been misdiagnosed as spider • Lymphomatoid papulosis effects. Even if bitten, spiders may not bites, include bacterial infections from Underlying disease states introduce any venom which results in a Staphylococcus or Streptococcus strains; • Diabetic ulcer dry bite. viral infections, particularly herpes or Vascular disorders • Focal vasculitis In a small percentage of cases, an shingles; fungal infections; lymphoma or • Purpura fulminans irregular red area develops around the lymphomatoid papulosis; lyme disease; • Thromboembolic phenomena bite area within 2 to 8 hours and the site diabetic ulcers; and poison ivy to name • Polyarteritis nodosa becomes painful and itchy. A small blister just a few (Table 2). One of the most likely Miscellaneous/Multiple causative agents • Pyoderma gangrenosum may develop at the bite site. Typically this causes of such dermonecrotic lesions in is a • Pressure ulcers heals normally with no further effects. bacterial infection known as Community- • Stevens-Johnson syndrome In a small fraction of these cases, further Acquired Methicillin-Resistant • Erythema multiforme • Erythema nodosum complications can develop. A bluish sinking Staphylococcus aureus (CA-MRSA). • Toxic epidermal necrolysis patch, with the central blister, may occur CA-MRSA outbreaks are occurring with • Lyell syndrome within 24 to 72 hours after a bite. This may ever increasing frequency throughout the progress into an irregular lesion, an inch or country in hospitals, prisons, and among two in diameter, with surrounding redness members of athletic teams. This bacterial often be seen amongst dense shrubs, on homes, these spiders are almost always lawns, and in corners of a house. found in basements. Outdoors they may be Funnel weavers also very commonly common under rocks and around gardens. enter homes. Indoor migrations are greatest This European spider feeds on isopods – in late summer and early fall as the mature sowbugs or the pillbug (a.k.a. ‘roly poly’). spiders wander in search of mates and This is one of the very few spiders, cooler outdoor temperatures. The majority along with the recluse spiders, that also of these migrants are males, which possess have three pairs of eyes. These are densely conspicuous, paired bulbous structures clustered in a small area in the center of the from the head region that superficially may head, not spread out on the cephalothorax appear as fangs. However, these structures in three pairs as with the recluse spiders. are pedipalps, used only to transfer sperm. However, the following features are useful Funnel weaver spiders are the group to distinguish these from recluse spiders: Figure 11: Wolf spider, Pardosa sp. most commonly mistaken for recluse very large jaws tipped with long fangs; spiders in Colorado. However, they can cephalothorax and legs uniformly colored readily be distinguished based on several reddish brown; and the abdomen is features: body is hairy; four pairs of uniformly of lighter brown or tan color. eyes; and legs that are often are banded Running crab spiders or patterned. (Philodromidae). The running crab Funnel weaver spiders common in the spiders are active hunters normally found state usually are in one of three genera: searching for insect prey among plants, Tegenaria spp., Agelenopsis spp., Hololena but they occasionally wander into homes. spp. Particularly common around homes Their body form is somewhat similar to the in Colorado are the species Tegenaria more common crab spiders (Thomisidae domestica, Agelenopsis pennsylvanica, and family) with a generally rounded abdomen Hololena hola. and the front two pairs of legs being longer Cellar spiders (Pholcidae). Cellar than the others. (The second pair is always spiders are very longlegged spiders found the longest.) They are variable in color but almost always in association with a some have dark markings that may cause web. (A common name for the family is confusion with the violin pattern of the daddylonglegs spiders, although this causes recluse spider. The running crab spiders confusion with the arachnids in the Order can be distinguished from recluse spiders Figure 12: Wolf spider, Schizocosa sp. Opiliones, commonly called daddylonglegs, by: second pair of legs is longer than which are not spiders.) Webs are produced the other legs; four pairs of eyes, in two in dark corners of basements, garages and rows; somewhat flattened body form; and outbuildings. An interesting behavioral dorsal marking, if present, is often located aspect is that often these spiders will on the abdomen and is not distinctly a bounce in the web when disturbed. violin pattern. Confusion of these spiders with the Two genera of running crab spiders brown recluse sometimes occurs because of most commonly cause confusion with patterning that may be found on the body, recluse spiders, Philodromus spp. and superficially resembling the violin pattern Thanatus spp. Those that are most notable on the brown recluse. However, the commonly found in homes are Philodromus cellar spiders commonly encountered can cespitum and Tibellus oblongus. readily be distinguished based on several Wolf Spiders (Lycosidae). The wolf Figure 13: A sunspider, Eremochelis bilobatus. features: very long legs; body form that is spiders are active hunters and often are longer than wide; eight eyes, often in two among the most common spiders found recluse spiders by several features: four clusters of three eyes with a pair of eyes crawling around yards and gardens. They pairs of eyes with the two upper pair much in between; and they are almost always do not produce webs for prey capture, but larger than the lower pair ; hairy body associated with a web. physically overpower insect prey. After an form; and an abdomen that is longer than The two types of cellar spiders found egg sac is produced, females carry it, and it is wide. in Colorado that are sometimes mistaken attach it to the tip of the abdomen. The most commonly encountered for brown recluse are Pholcus phalangioides Most wolf spiders are drab colored, species around homes are those in and Psilochorus spp. but some may have darker patches on the the genera Pardosa and Schizocosa. Wood louse hunters (Dysderidae). body. These typically are in the form of two Occasionally, very large spiders in the Along with funnel weavers, the wood louse longitudinal stripes, but they are sometimes genus Hogna – the giant wolf spiders – are hunter, Dysdera crocata, is also commonly confused with the violin pattern of the encountered. mistaken for a brown recluse. Within recluse. Wolf spiders can be separated from Sunspiders (Order Solifugae). Dominguez, T.J. 2004. It’s not a spider bite, Sunspiders are not true spiders (Order it’s Community-Acquired Methicillin- Araneae) but placed in a different arachnid Resistant Staphylococcus aureus. Journal order, Solifugae. Other common names for of American Board of Family Practice these bizarre-looking arachnids include 17(3):220-226. wind scorpions and solpugids. Species Maretic, Z. 1987. Spider Venoms and their found in the Middle East are sometimes Effects. In: Ecophysiology of Spiders known as camel spiders. (ed. W. Nentwig), Springer-Verlag, New Sunspiders are readily distinguishable York, pp. 142-159. from spiders by the presence of long leg- Vetter, R.S. 1999. Identifying and like pedipalps arising from near the front of misidentifying the brown recluse the body. This gives them the appearance spider. Dermatology Online Journal of having five pairs of legs. Sunspiders 5(2): 7, http://dermatology.cdlib.org/ also have a very large cephalothorax with DOJvol5num2/special/recluse.html prominent forward-projecting jaws. These Vetter, R.S. 2000. Medical myth: idiopathic are used to capture and crush insect prey. wounds are often due to brown recluse Sunspiders do not possess venom glands. or other spider bites throughout the United States. Western Journal of Medicine 173:357-358. References Vetter, R.S., P.E. Cushing, R.L. Crawford & Benoit, R. & J.R. Suchard. 2006. L.A. Royce. 2003. Diagnoses of brown Necrotic skin lesions: Spider bite–or recluse spider bites (loxoscelism) greatly something else? Consultant. Volume outnumber actual verifications of the 46 (12). October 1, 2006 http:// spider in four western American states. consultantlive.com/showArticle. Toxicon 42:413-418. jhtml?articleID=193105532

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