COMMON AND SCIENTIFIC
Over the years, the group of spiders
to which the brown recluse belongs has been known by various colloquial
names: "violin" spiders, "fiddleback" spiders, "recluse" spiders,
and "brown" spiders. Recently the American Arachnological Society
chose "recluse spiders" as the official common name for this group.
The scientific name for the recluse spider group is Loxosceles
(lox-SOS-a-leez). All known members of the group have a scientific
name, and the more familiar members of this group also have a common
name (e.g., brown recluse, desert recluse, Arizona recluse).
QUCIK and SIMPLE IDENTIFICATION OF
BROWN RECLUSE SPIDERS
Large Brown Recluse Spiders: about
the size of a quarter, including its legs. Small ones: size of a
dime. Note that the "VIOLIN" part is very difficult to
see. You may need a magnifying glass. Thi photo shows a recluse
in its typical resting posture -- look at the legs and how they
It's NOT a Brown Recluse IF
any of the following are true:
1) It's really BIG:
A spider's body is in two main parts. The size of the body, not
including legs, of a recluse is smaller than a dime.
2) It's really HAIRY:
Brown recluses have only very fine hairs that are invisible to
the naked eye.
3) It JUMPS:
Jumping spiders live up to their name, and some other spiders
including wolf spiders occasionally jump, but recluses don't.
4) I found it in a WEB
Brown recluses don't spin a web to catch prey; they spin silk
retreats and egg cases, but don't form a typical recognizable
5) It has DISTINCT MARKINGS VISIBLE TO THE
NAKED EYE, such as stripes, diamonds, chevrons, spots,
etc. that are easily seen.
Brown recluses have no markings on their legs or abdomen (the
largest part of the spider's body). The "violin" is
very small and located on the front half of the body. The violin
is also indistinct in some, especially young spiders. They're
really rather dull looking.
BETTER IDENTIFICATION OF BROWN RECLUSE SPIDERS
The most definitive physical feature
of recluse spiders is their eyes:
Most spiders have eight eyes that typically
are arranged in two rows of four but recluse spiders have six equal-sized
eyes arranged in three pairs, called dyads. There is a dyad at the
front of the cephalothorax (the first main body part to which the
legs attach) and another dyad on each side further back.
Many publications refer to the violin on
the dorsal surface of the cephalothorax as the most important
Although this marking is fairly consistent in mature
brown recluses and Texan recluses (L. devia), it can vary
in intensity and sometimes fades in preservative, and it is very
faint to nonexistent in several recluse species found in the southwestern
United States (e.g., the desert recluse). Therefore, checking the
eye pattern will eliminate almost all suspect recluse spiders from
consideration whereas the presence or absence of the violin marking
may lead to misidentifications. In addition, the abdomens of all
recluses are covered with fine hairs and are uniformly colored,
although the coloration can vary from light tan to dark brown, depending
on what they have eaten. There is never a coloration pattern on
the abdomen. Finally, the legs are similarly covered with fine hairs
whereas many nonrecluse spiders have stout spines on their legs.
Because of the misinformation surrounding
the brown recluse's presence, many spiders that are virtually harmless
are turned in by the public for identification, but most of them
are not even from the recluse family. In California, the few Loxosceles
spiders that have been turned in for identification were the desert
recluse (not the brown recluse) and, not surprisingly, were found
in the eastern deserts where they are native. Presented below are
descriptions of spiders that share some of the same physical features
as the brown recluse and might be misidentified as a recluse spider.
The spitting spiders (Scytodes
spp.) are closely related to recluse spiders and have six eyes arranged
in a similar pattern. However, they also have many black spots or
lines on their bodies that would exclude them as recluses. The woodlouse
spider, Dysdera crocata, has six eyes arranged in two groups
of three (triads) and no bodily markings; nonetheless, it is commonly
mistaken for a recluse in California and in other parts of the United
Spiders with Violin-Shaped or Other Dark Markings
Many common tan or gray spiders have
dark markings on the head region, which convinces people that they
have caught a bona fide recluse spider. These spiders include cellar
spiders (Psilochorus spp., Physocyclus spp.), pirate
spiders (Mimetus spp.), and sheet web spiders (Linyphiidae).
The marbled cellar spider, Holocnemus pluchei, also confuses
people even though the dark marks are on the ventral (underside)
not the dorsal (top) surface of the body.
Ubiquitous Brown Spiders
Virtually every spider that is tan
or brown has been turned in as a potential brown recluse. There
are hundreds of species of these spiders in California. They include
ground spiders (Gnaphosidae), sac spiders (Cheiracanthium
spp., Trachelas spp., and many of the liocranoid spiders),
wolf spiders (Lycosidae), grass spiders (Agelenidae), orb weavers
(Araneidae), and male crevice spiders (Filistatidae). More specifically,
males of both the western black widow (Latrodectus hesperus)
and the false black widow (Steatoda grossa) are frequently
brought in for recluse verification. All of these brown spiders
have eight eyes and can quickly be eliminated from consideration.
Eleven species of recluse spiders are
native to the United States and a few non-natives have become established
in circumscribed areas of the country. The brown recluse spider
is the proper common name for only one species, Loxosceles reclusa.
It is the most widespread of the North American recluse spiders
and lives in the south central Midwest from Nebraska to Ohio and
south through Texas to Georgia.
Life History Characteristics
Recluse spiders, as their name implies,
are reclusive. These nocturnal spiders emerge from their retreats
at night and actively hunt down prey or may wait for prey to land
in the small area several inches from their retreat. Although they
do not build webs to capture prey, they do use silk to build a retreat
in which they hide during the day. As dawn approaches, they may
seek shelter in dark places such as clothing or shoes. Also, mature
males roam in search of females. It is these two behaviors that
can bring them into contact with people.
In nature, recluses are found in cracks and crevices
in and under rocks. Recluses have very much benefited from human-altered
environments where they are readily found under trash cans, plywood,
tarps, or rubber tires, in boxes, etc. They are synanthropic (found
in association with humans) and therefore are considered a "house"
spider. In fact, in South America the recluse species have common
names that translate as "the spider behind the picture" or "the
spider in the corner."
Recluse spiders are relatively long lived. Among
the various species, they mature after about 1 year and average
a 2- to 4-year life span with some living more than 7 years under
laboratory conditions. They are also well known for surviving long
periods (6-12 months) without food before perishing.
Abundance of Recluses
One consistent life history characteristic
of recluse spiders is that in the right environment their populations
are usually dense. Loxosceles reclusa is a common house spider
in the midwestern United States. If you find recluses, you do not
find one, you find many. Examples for the brown recluse include
9 under a piece of plywood in Oklahoma, 52 in an indoor laboratory,
and 6 under a waterbed frame in Arkansas, 150 in a Kansas home,
40 collected in a Missouri barn in 1 hour, and 44 in sticky traps
in a Tennessee home in 1 day.
Unlike many other spiders that disperse by either
migrating or being carried by air currents when small ("ballooning"),
recluse spiders can only expand outside their native range as a
result of human intervention. There are fewer than 10 documented
cases of the spider being collected in California, spanning more
than 4 decades, typically in facilities that receive goods from
out of state. Searching the immediate area yielded no additional
brown recluses and therefore they were considered to be individual
stowaways. Undoubtedly, more brown recluses have been inadvertently
brought into the state via commerce and the relocation of household
belongings; however, amazingly few specimens have ever been collected.
Never have any of these translocated spiders been able to establish
a foothold and start a population in California. Considering that
there are millions of brown recluses cohabiting with people in the
southcentral Midwest and brown recluse bites are only an occasional
occurrence there, California does not have anywhere near sufficient
populations of these spiders to be responsible for the number of
cases or illnesses that are attributed to them.