Arachnids Submitted as Suspected Brown Recluse Spiders (is ON topic if you read it)
- From: "CaliforniaLyme" <CaliforniaLyme@xxxxxx>
- Date: 10 Jul 2005 08:13:19 -0700
http://spiders.ucr.edu
Arachnids Submitted as Suspected Brown Recluse Spiders (Araneae:
Sicariidae): Loxosceles Spiders Are Virtually Restricted to Their Known
Distributions but Are Perceived to Exist Throughout the United States
J. Med. Entomol. 42(4): 512-521 (2005)
RICHARD S. VETTER
Department of Entomology, University of California, Riverside, CA
92521; and Biology Division, San Bernardino County Museum, 2024 Orange
Tree Lane, Redlands, CA 92374
J. Med. Entomol. 42(4): 512Ð521 (2005)
ABSTRACT An Internet offer was made to identify any spider in the
United States perceived to be a brown recluse spider, Loxosceles
reclusa Gertsch & Mulaik (Sicariidae). In total, 1,773 arachnids from
49 states represented three orders (Araneae, Solifugae, and Opiliones)
and the identiÞable spiders (Araneae) consisted of 38 families, 88
genera, and 158 recognizable species. Participants from states at least
half within the known brown recluse distribution submitted Loxosceles
spiders 32Ð89% of the time, except Louisiana and Mississippi with no
submissions. From 25 of 29 states completely or almost completely
outside of the range of Loxosceles spiders, no recluse spiders were
submitted. Only two discoveries of brown recluses and two of the
worldwide tramp species Loxosceles rufescens (Dufour) were submitted
from nonendemic Loxosceles areas. States on distribution margins of
brown recluse or other native Loxosceles spiders were intermediate in
their Loxosceles submissions. This study showed that 1) the general
public perceives brown recluses to occur over wide-ranging areas of the
United States; and 2) brown recluses are frequently submitted from
endemic states and almost never from nonendemic states, and therefore
are virtually limited to their known distributions. This study
corroborates opinions that diagnosis of brown recluse spider bites is
best restricted to areas historically supporting proven, widespread
populations of Loxosceles spiders.
KEY WORDS Loxosceles reclusa, Arachnida, misidentiÞcations,
distribution
ALTHOUGH BROWN RECLUSE SPIDERS, Loxosceles reclusa Gertsch & Mulaik
(Sicariidae), are historically limited to the central and south central
United States, their reputation causes people to assume that they are
routinely found throughout North America. This spider was Þrst
associated with necrotic skin lesions in the United States by Atkins et
al. (1957). The distribution of populations of L. reclusa is well
demarcated from southeastern Nebraska through the southernmost strip of
Ohio and south into Texas to northern Georgia and western South
Carolina (Gertsch and Ennik 1983; Vetter 2000; Swanson and Vetter 2005;
unpublished data). There are 10 additional native Loxosceles species in
the United States, five having signifcant distributions (Gertsch and
Ennik 1983, Swanson and Vetter 2005). Two exotic species, Loxosceles
rufescens (Dufour) and Loxosceles laeta (Nicolet), also are
sporadically found within the United States. L. rufescens, originating
from the Mediterranean region, is rare but scattered across the United
States. L. laeta, originating from South America, is known to have
tightly circumscribed populations in cities in urban Los Angeles Co.,
California; one house in Polk Co., Florida, and the basement of the
Museum of Comparative Zoology at
Harvard University, Cambridge, MA (Gertsch and
Ennik 1983, Vetter et al. 2004). Although there are
suspected variations in virulence among the species,
all Loxosceles spiders should be considered potentially
capable of producing dermonecrosis to some extent.
Since 1957, the infamy of the brown recluse and
other Loxosceles species has spread such that diagnoses
of brown recluse spider bites are commonly
made throughout North America where recluse spiders
are rare or have never been found (Russell and
Gertsch 1983; Russell 1986; Vetter 2000; Vetter and
Bush 2002a, b; Vetter et al. 2003, 2004; Bennett and
Vetter 2004; Swanson and Vetter 2005). In addition to
medical misdiagnoses, this misconception of brown
recluse spider presence continues to be perpetuated
by hyperbolic and unsubstantiated news media reports
of alleged bites or alleged recluse sightings outside
its endemic range and an anxious general public
believing erroneous word-of-mouth. This misconception
is further entrenched by the misidentification of
common harmless spiders as brown recluses by nonarachnologists.
Many members of the general public and the medical
community suggest that alleged brown recluse
snip
0022-2585/05/0512Ð0521$04.00/0 2005 Entomological Society of America
.
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