GOT RECLUSES?

Have you (or your customers) misidentified brown recluse spiders in the past? You may be surprised at the answer.

There are thousands of species of spiders in the United States, however, the average American is only familiar with two: the black widow and the brown recluse. The infamy surrounding these spiders is widespread due to tales, hyperbolic or otherwise, of their poisonous bites which have potential for severe debilitation and, in very rare cases, death. The black widow is somewhat less problematic from a pest control viewpoint because its characteristic coloration of shiny black body with ventral red hourglass makes it readily recognizable by the untrained person.

However, despite this, other spiders (female false black widows and immature bold jumping spiders, Phidippus audax) are sometimes confused with black widows. In contrast, the brown recluse is not as easily discernible by physical appearance and many different arachnids (some not even spiders) are misidentified as recluses by the general public, the medical community and PCOs. Because of misidentifications, hyperbolic media stories and medical misdiagnoses, the American public believes that the spider can be found throughout the United States.

In truth, the brown recluse is restricted almost solely to its native distribution. Although recluse literature always forebodingly states that they can be transported out of their range, brown recluses are extremely scarce and rarely — if ever — have they been successful at establishing a breeding population elsewhere. Despite all the hoopla that surrounds the discovery of a single brown recluse in the eastern seaboard, northern Midwest or Western states, typically this one spider is an itinerant that has been intercepted and does not represent a massive population outside its range.

RECLUSE SPIDERS. The brown recluse is the common name for one species of spider, Loxosceles reclusa. The genus name means "slanted legs" (probably named for the way it rests) and is pronounced similar to "isosceles," like in the triangle from that horrid math class years ago. It lives from Nebraska south through Texas and east to the southernmost edge of Ohio and south to Georgia. There are 10 additional Loxosceles species in the U.S. with 5 having somewhat extensive distributions and the other 5 being known from only a few localities. Two non-native species are present in the U.S. as well.

The south American violin spider, Loxosceles laeta (LEE-ta), has populations in basements and steam tunnels in a small pocket of urban Los Angeles, Calif., and possibly still lives in the basement of the Harvard University museum in Massachusetts as was reported in the past. A Mediterranean recluse, Loxosceles rufescens, seems to vagabond its way around the world and shows up in various cities around the United States, again often as single itinerants. All recluses are considered to have venom capable of causing wounds in humans and should be regarded with care.

ENDEMIC AREAS. One thing is true for recluse spiders of any species: when they find a habitat conducive to their survival, they are almost communal and you can easily collect many specimens. Regarding the brown recluse, it is not uncommon to find several spiders a week in a typical urban home within its range, where an occasional house supports more than 100 recluses at the same time. In a study done in Chile, 29 percent of the homes contained the south American violin spider with the five greatest infestations averaging 163 spiders (range 106 to 222 spiders).

Although these high infestation rates would probably give anyone the creeps, rarely do people suffer spider bites from these dens. The brown recluse is "synanthropic" which means that it increases in numbers when associated with humans. It is a common house spider in its range, yet the human population of the Midwest is living with millions of these spiders and many households never experience a bite. Although there are many similarities among the various Loxosceles species, there are also differences. The brown recluse is an urban pest while other native American species seem to be less so. The latter are typically found in the arid Southwest, only infest homes that are surrounded by natural vegetation and are not often found in urban homes.

NON-ENDEMNIC AREAS. Outside the native range in the United States, recluse spiders are extremely rare. Although the spiders do occasionally get transported around, populations of transplanted species are virtually non-existent. When it does happen, often the infestation is limited to one building (or several if interconnected by underground conduits). Unfortunately, this knowledge appears to be only well known to those few people who work with spiders as a significant part of their employment (arachnologists, vector control personnel and some, but not all, PCOs). The rest of the U.S. human population is thoroughly convinced that brown recluses are everywhere, running around causing midnight mischief, inflicting wounds and then evaporating into the night, never to be seen again.

This perpetual myth is kept alive by several aspects. First, speculative news stories are published, based on the possibility not probability of a recluse spider being found in a local area. Second, medical misdiagnoses are made of a variety of conditions (bacterial, fungal, viral, cancer, bites from blood-feeding insects, Lyme disease, poison oak/ivy, chemical burn) that look very similar to the spectrum of wounds caused by actual recluse envenomation. Third, the public’s erroneous word-of-mouth, fed by arachnophobia, the media and the medical community, keeps the myth alive. Compounding this myth is that any brown creature with eight legs is all too often misidentified by the average homeowner as a brown recluse, which reinforces their erroneous opinions.

Even though both popular and medical literature continue to discuss how easily brown recluses are transported around the country, the lack of extension of their range is rather puzzling. However, one must remember that brown recluses evolved on this continent; hence, they are restricted to their range by a multitude of environmental conditions, predators, parasites and competition from creatures of similar ecological habits. Arthropods that disperse successfully across a continent are typically non-natives, flourishing in the absence of these regulatory pressures. Well-known examples include Africanized honey bees, red imported fire ants, Mediterranean fruit flies, German yellow jackets, many species of cockroaches and termites, just to name a few. Even among spiders, continental colonization is achieved more commonly by non-natives (e.g., woodlouse spider (Dysdera crocata), false black widow (Steatoda grossa), mouse spider (Scotophaeus blackwalli) cellar spider (Pholcus phalangioides), barn funnel spider (Tegenaria domestica)) than by natives.

IDENTIFYING RECLUSE SPIDERS. Virtually everything written about recluse spider identification gives a "Reader’s Digest" version of the salient ways to identify a spider as a brown recluse. However, as with many things, the more you know, the more you realize that it isn’t all that simple. It is often mentioned that you can tell a brown recluse by the violin pattern on its head region (ie., cephalothorax). Although this is straightforward when you see a recluse, there are many other harmless spiders that have darkened coloration in the same area and they are creatively mistaken for recluses. These spiders include many cellar spiders (family Pholcidae) and pirate spiders (family Mimetidae) and the tiny Oecobius spiders.

In addition, immature and newly molted brown recluses may not have a well-defined violin. Adding more confusion is that the violin pattern of many western Loxosceles species is often indistinct or missing, where the pattern is often formed by hairs and not underlying pigmentation. Therefore, it is possible for a person in the Southwestern United States to identify a harmless spider as a recluse and a recluse as a harmless spider.

A more precise method requires a hand lens or magnifying glass to count the eyes, although once you see the eyes magnified, it should no longer be a problem to see the eye pattern without optic aids. Most spiders have eight eyes in two rows of four whereas recluse spiders have six eyes arranged in one row of couplets or pairs. There is one pair near the front of its cephalothorax and a pair on either side. If you draw a line through the eyes, it would make a U-shape with the open end toward the back. Rarely does an identification guide continue to tell you that there are additional harmless spiders (spitting spiders, family Scytodidae) that have the same eye pattern but usually are covered with black spots or lines. Spitting spiders are much more widespread in the U.S. than are recluses. Yet despite this relatively simple method to identify recluse spiders, most of the American public cannot identify a recluse if it bit them. This is even truer when outside the endemic range of recluses where a multitude of non-recluse spiders are misidentified.

CONTROL. In controlling recluse spiders, the specimens running about or captured on sticky traps are typically males and spiderlings. The females are the true "recluses" preferring to remain in cracks and voids, rarely venturing out. For this reason, any treatment strategy relying primarily on surface (baseboard) and/or space (ULV) treatments is doomed from the start. The proper strategy to employ for this spider is painstaking treatment of cracks and voids with a residual dust insecticide from the attic to the basement or crawlspace (if present). These spiders commonly follow plumbing pipes and electrical wires to travel from area-to-area and room-to-room within a structure. Focusing treatments on voids where these "structural guidelines" run is a key tactic. Additionally, the cracks behind all baseboards and door/window frames require treatment with the selected dust product (Drione and DeltaDust both work well).

It is important to use a vacuum to remove spiders, egg sacs and webbing as these are discovered in and under furniture, within boxes, etc. Spot treatments along baseboards behind furniture are helpful for controlling wandering males and spiderlings. Also, one cannot place too many monitoring traps. Each spider captured is one that potentially cannot come into contact with a person. In addition, the outside is very important as exterior cracks need to be treated and potential harborages (e.g., thick ground cover, piles of items) need to be eliminated.

Finally, the customer needs to understand the steps they can enact to avoid potential bites. They also need to be advised that one service is not likely to solve the problem. In some, if not the majority, of cases, total elimination is impossible. Spider populations can be markedly reduced, but an occasional spider may still be seen. Monitoring traps help by capturing most spiders. Regular service visits for a number of months up to a year or longer are necessary, depending on the severity of the original infestation.

THE GOT RECLUSES? CHALLENGE. Besides the educational material presented here, this article also launches the "Got Recluses?" Challenge. The senior author is interested in embarking on a study to identify spiders in reference to recluse distribution in the U.S. and the ability/inability of the American public to properly discern potentially dangerous recluse spiders from the harmless ones. This study has several thrusts of interest.

• To determine if the current range of the brown recluse is similar with that historically known to arachnologists.

• To determine what spiders the American public identifies as brown recluses, whether they are correct or incorrect.

• To determine if there are any populations of recluses outside of their native range

• To determine whether these non-endemic populations are the brown recluse or possibly one of the non-native species instead. (Recently the senior author received many recluse specimens from New England, where the PCO had been calling them brown recluses for years. They were actually the Mediterranean recluse, which means that this becomes an issue of establishment of a non-native rather than range expansion of a native species.)

THE GOT HOBOS? CHALLENGE. Also, the hobo spider, Tegenaria agrestis, has been getting lots of publicity in the last two decades as a dangerous spider. However, if you think the public has trouble identifying brown recluses correctly, wait till you see what will be done with hobo spider misidentification. Although a hobo spider makes a funnel-web (a trampoline-like sheet that tapers back into a hole in which the spider sits), so do about 100 other species of similarly-colored spiders in the United States, including several harmless Tegenaria species. However, already the public (and PCOs, too!) have seen these webs and assumed they have hobo spiders. The only way one should verify a hobo spider, unless extremely experienced with them, is comparison of their genitalia to scientific illustrations.

The hobo spider is found in the Pacific Northwest east to Montana and south to Oregon and northern Utah. Currently there is no definitive publication describing the known range of hobo spiders. Because of all the misidentifications, they possibly are much more limited in their distribution than previously thought. Also, population dynamics change; hobo spiders used to be common in Seattle but have since been displaced by a harmless, larger cousin, Tegenaria gigantea, which is almost identical to a hobo spider. Therefore, this study would also like to determine the distribution of hobo spiders in the western U.S.

If you are interested in helping out with this research, please fill out the form (http://www.pctonline.com/features/feature.asp?ID=117) and mail it and the spider(s) to the address listed here. Feel free to photocopy the form and send in as many spiders as qualify for the Challenge. In order for a spider to be considered part of the study, the spider must be submitted by a client with the magic words "is this a brown recluse spider" or "I think this is a brown recluse" (or hobo spider) or some other permutation close to it. Or if you, as a pest professional, have a spider you think might be a brown recluse or hobo spider and just aren’t sure. If a client from an endemic area gives you a spider that you know is a recluse spider, it would be appreciated if you send it because this will be serving as a comparison group to non-endemic submissions. Areas along the margins of the ranges will be of special interest. For example, although about half of Iowa is included on the map here, a more definitive publication says that the brown recluse has only been documented in 12 of its 99 counties. Other areas just north of the historical brown recluse range are of interest as well to determine if there is northern range expansion in light of recent comments regarding global warming and climate change. Also, if you live outside the native range of recluses and have recluse specimens from years past, it would be of great interest to see them to determine whether they are the brown recluse or another related species. All recluses from outside endemic areas will be returned to you after examination. Please only send those in association with recluse or hobo spider determination; don’t send random spiders.

• Send spiders preserved in a small amount of rubbing alcohol or ethanol in leakproof containers to the address listed on the form.

• Use one form for each spider. (Or, one form and one container if spiders are collected in the same house/area on the same day. Two spiders from the same house on different days would require two forms and two containers.)

• Include a contact address, preferably email so you can be contacted easily

• If you wish to send glueboards or sticky traps, wrap each in plastic and send the whole thing in a plastic bag.

Realize that this article may inspire an inundation of hundreds of spiders so a quick reply may not be possible. The senior author will return any recluse that is found from outside the known ranges. Other spider returns will depend on demand and fund availability. The study will probably terminate after 2000+ spiders are received and the results will be published in PCT magazine as well as a peer-review entomology journal.

Editor’s note:  Do not send spiders in alcohol unless you follow the regulations for mailing flammable liquids. It may be better to preserve the spider in alcohol for a week and transfer it to a leakproof container filled with water the day of shipping (mark the package "package contains water.") Dead spiders can be sent also if carefully packaged, however, it will be more difficult to identify them when desiccated.

The authors are a professor at University of California, Riverside and technical director, Terminix International, respectively. They can be reached via e-mail at rvetter@pctonline.com or shedges@pctonline.com.