![]() Nine protein fractions have been identified in the venom with most attention given to the enzyme sphingomyelinase D, considered the main contributor to cell injuries resulting from bites by these spiders. Most, if not all, of the recluse spiders have venom that can cause tissue death (cytotoxins). Occasionally it is transported out of its normal range, but it rarely survives and establishes outside the area. It occurs in many of the midwestern and south central states, and can be very common in and around homes in eastern Kansas, Missouri, Arkansas, Louisiana, Oklahoma, parts of Texas, and some other states. is the brown recluse, Loxosceles reclusa. The best known of the recluse spiders found in the U.S. Specimens of Loxosceles that are collected from Colorado currently can be identified by personnel at the Denver Museum of Nature and Science. Identification of the various Loxosceles to the species level can only be done by an expert. laeta is established in a few localized areas on both coasts. In addition, the Mediterranean recluse, Loxosceles rufescens, is occasionally introduced and likely now established in many parts of the country, although nowhere is it considered to be common. with most confined to areas of southwestern states bordering Mexico. There are 10 native recluse spiders ( Loxosceles spp.) in the U.S. Brown recluse spider showing the violin pattern on the cephalothorax. Webs are not produced in open areas where they are readily seen.įigure 2. Uniformly colored, without any banding or patterning Silky appearance due to fine hairs no spines present.Īctive at night restricted to web-lined refugia during day. Overall color uniformly brown, without any patterning. Overall color uniformly brown Darker brown pattern in center, somewhat resembling a violin, usually present. Features to identify recluse (brown) spiders ( Loxosceles species).ģ pairs, of approximate equal size, arranged in semicircular pattern. where they are common, recluse spiders found in homes are often found in basements. ![]() During the day they hide in dark crevices and hollows. ![]() The legs are uniform in color, never banded. The legs have a silky appearance, covered with fine hairs and large spines are not present. Legs of recluse spiders are long and thin. (Brown patterning on the cephalothorax also occurs in many Colorado spiders, including funnel weavers and cellar spiders.) The contrast intensity of this pattern can vary among the different recluse species and life stages. This is typically described as a “violin pattern” and the eyes are incorporated into the base of it. On the cephalothorax (the body region including the head and legs) a brown marking is usually present. The abdomen is uniformly colored, without patterning. Overall body color is brown, which may range from a light to dark brown. The arrangement of the eyes on the recluse spiders is one pair in the front, the other two along the sides, forming a semicircle. Overwhelmingly, most spiders found in Colorado have four pairs. ![]() Recluse spiders have three pairs of eyes, a very unusual feature among spiders. The quickest way to positively identify if a spider might be a recluse spider is to examine the arrangement of the eyes. (Photo courtesy of the University of Nebraska.) Identification Figure 1.Brown recluse spider. However, close examination can readily distinguish them (see Table 1). Unfortunately, also greatly overdiagnosed are purported spider bites caused by brown recluse spiders – a situation perpetuated by many in the Colorado medical establishment as well as through self-diagnosis.Ĭolorado hosts a great many kinds of spiders that are brown or have some patterning that may superficially resemble brown recluse spiders. Funnel weaver spiders and wood louse hunters are the two groups most commonly mistaken for recluse spiders.īrown recluse and related recluse spiders ( Loxosceles spp., Family Sicariidae) are, by far, the most commonly misidentified spiders in Colorado.Brown recluse spiders usually have a “violin pattern” on the cephalothorax.The quickest way to positively identify a recluse spider is to examine the arrangement of the eyes – there should be three pairs.Colorado has many kinds of spiders that are brown or have patterning that may resemble brown recluse spiders.
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