BACK TALK

RECOUNTING RECLUSES
As an entomologist who has worked in this industry for three decades, I read Rick Vetter’s article (“If It Isn’t A Spider Bite What Is It?” May 2002) with interest. I agree that many bites are misdiagnosed and blamed on spiders, particularly the brown recluse. However, having worked on an undergraduate degree with distinction thesis, The Spiders of Delaware, and a graduate thesis dealing with spiders, and written The Spiders of Indiana while at Purdue, I have some information that may be of interest.

There is a species of “brown recluse” that does occur naturally in buildings on the East Coast. It is Loxosceles rufescens, which packs the same kind of wallop as the true brown recluse spider. I have found substantial populations of this species living in the basements of the Trinity Church real estate office across the street from Trinity Church in New York City. Since that finding, Lou Sorkin of the American Museum of Natural History in New York has found others.

I have also found it in Philadelphia at the Pennsylvania Academy of the Fine Arts, the University of Pennsylvania Museum and the basement of the office building of the Philadelphia District Attorney. I am not absolutely certain, but I believe many of the underground steam tunnel systems and perhaps the subway tunnels of Philadelphia have resident populations of this spider. If a diagnosis of a “brown recluse” spider bite were made in New York City or Philadelphia, I would not dismiss it out-of-hand as a misdiagnosis.

A local pest control operator, John Amendt of Amendt Pest Control, and I have worked for several years to rid the Pennsylvania Academy of the Fine Arts of this infestation. In addition to lots of glueboards and spraying with a residual encapsulated insecticide, we have sealed up many spider highways into the building from the steam tunnels that run parallel to this building immediately outside the foundation. The Broad Street Subway also runs along this foundation. I have personally supervised the same kind of approach at the University of Pennsylvania Museum, where it was fairly obvious that the spiders were gaining access to a basement storeroom from an adjacent steam tunnel. An intensive glueboard program has apparently been successful in eliminating infestation in other parts of the basement level of this structure.
Thomas A. Parker
President, Entomologist
Pest Control Services Inc.
Lansdowne, Pa.

VETTER’S RESPONSE
I would like to correct two mistakes in the above letter. First, there is only one “brown recluse,” which is the accepted common name for Loxosceles reclusa. L. rufescens is indeed a recluse spider (an accepted common name for the genus) but it is not a brown recluse. Secondly, Loxosceles rufescens does not occur naturally anywhere in the United States. It is a non-native (Mediterranean) spider. It is, in fact, found in several U.S. cities but each is typically a spot infestation of this non-native species in a foreign environment. I have seen multiple specimens from Michigan; Boston; Washington, D.C.; Fresno; and Spokane and it is not surprising to find them elsewhere. However, this is not cause for alarm or hyperbole.

As is typical of Loxosceles species in non-endemic regions, it does not spread far from its point of colonization — like an unchecked bacterial infection. For example, the Michigan population is only known from the basement of one building on a university campus. Similarly, in heavily populated Los Angeles County, a reliable infestation of Loxosceles laeta exists since 1967. The spiders are easily found in places known to have them, yet they aren’t in homes, no one is being bit by them, no homeowner has turned a specimen in for verification (even though the area recently publicized and held a county-wide spider survey). The Department of Health considers them a minimal health risk.

The problem with the reporting of Loxosceles spiders in non-endemic areas is that it unleashes a predictable reaction: recluses are incorrectly claimed to be in homes and/or the cause of a myriad of wounds that have diverse non-arachnological origins, harmless spiders are misidentified as recluses (some by “authorities” [doctors, PCOs, county health officials] who obviously lack arachno-logical skills) and hyperbolic newspaper articles are published, all which reinforces medical misdiagnoses and public misconception. The emerging body of research is showing that many “brown recluse” bites are actually Lyme disease, anthrax, bacterial infection, chemical burn and about 25 other conditions. When the comment is made that it is possible to find Loxosceles spiders locally, then hundred-times more bite diagnoses erupt than the spiders could logistically cause. 

Along those lines, I just finished a study that has been provisionally accepted by a medical entomology journal. A Kansas woman collected more than 2,000 brown recluses in her house in six months, 400+ of which were envenomation-capable size. The four family members encountered recluses every week (and have lived there six years) and still not one bite. So I ask the rhetorical question: Why is it that people living with dozens to thousands of brown recluses don’t (or rarely) get bit, yet in areas of the country where recluses are rarely found and limited in distribution (or non-existent), bites are commonly diagnosed throughout a widespread area? When Loxosceles spiders are known to be living in a non-endemic area, more proof (recluses found at the “envenomation” locale) should be offered before considering a recluse bite to be a likelihood. Brown recluse bites are grossly overdiagnosed and in non-endemic areas have a low probability of being correct.
Rick Vetter
Department of Entomology
University of California, Riverside
Riverside, Calif.