Important Links related to the content of this page:
Related Links, regarding Brown Recluse Spiders on BugsInTheNews:
- Brown recluse Anatomy
- Brown recluse behavior; encounters in Joplin Missouri & Grove, Oklahoma
- Brown recluse encounter in Wichita Falls, Texas
- Brown recluse encounter near Lake Travis, Texas
- Brown recluse encounter in Collin County, Texas
On 29 April 2011 the following email was received from the owner of a relatively large three-year-old home, located in an upscale neighborhood in south Austin, Texas (78739):
My wife found this spider on top of some towels that were under the sink in our kids’ bathroom. It scared her pretty good but she killed it.
Is this a recluse? Or might it be a southern house spider, instead?
In the photos it sure looks like it has three eye clusters.
Thanks in advance for your help.
From the photos attached to this email it was obvious the spider was, as suspected, a brown recluse. Most of our native spiders are very beneficial, but not these. The males and females of the recluse spiders in the Sicariidae family produce a dangerously dermonecrotic venom and, like the black widow (whose venom is acutely neurotoxic), are not good spiders to have around.
Immediately, an appointment was scheduled for 2 May 2011, to inspect the house and determine if more of these spiders could be found. During that inspection, although remnants of the cribellate-like webbing typical of the brown recluse were observed, no live recluse spiders were seen.
That’s not a surprise.
Recluse spiders are, well… reclusive. Their numbers tend to increase in association with human dwellings, i.e., they are synanthropic, to the point that populations of the species tend to rise in association with humans, and are much reduced in the absence of such an association (Vetter, 2008, p.151), but they are not easy to find unless the home is absolutely infested with them, such that individual spiders have trouble finding places to hide that aren’t already loaded with other brown recluse spiders. This home was neat as a pin, and had absolutely no obvious clutter where brown recluse spiders could secret themselves away from the sight of humans armed with strong flashlights.
Still, it isn’t good to take chances with this species, so the home was sprayed with a non-toxic habitat modifier, to create an environment that would not nurture or attract brown recluse spiders or other arthropods. The homeowner was then shown how to repeat that process in order to carry out a habitat modification program that achieves PestAvoidance in and around the home, along with installing glueboard monitors to keep track of all the arthropods coexisting there. Over time, if these spiders are present — even in very small numbers — they should eventually show up on the glueboard monitors (but see the comments under UPDATES at the foot of this article).
The spider that had been found under the bathroom sink was collected, placed in a specimen bottle filled with 70% ethanol, and taken to the lab for microscopic analysis.
Under the microscope a number of measurements were taken of the spider’s external anatomy to confirm that it was, indeed, a brown recluse and not one of the other species in that genus (Austin is on the northern edge of the range of the Texas recluse (Loxosceles devia Gertsch & Malaik 1940), a recluse spider normally found south of here and into Mexico) that are sometimes found in this area.
Being a male, the pedipalps were measured as part of that process, and the morphology of the palpal tibia, cymbium, bulb and embolus was examined to confirm that these characters (see figs. 003-005) conformed to those described for Loxosceles reclusa (Gertsch & Ennik, 1983, p. 283-289). Specifically, it was found that the embolus (the long, narrow, needle-like projection extending from the bulb in figures 004 and 005) was 1.7 times the width of the bulb it projected from. In L. reclusa the embolus is much longer than the width of the bulb, as in this specimen, while the embolus of L. devia, though longer than the width of the bulb, is not remarkably longer (Gertsch & Ennik, 1983, p. 289-291).
Note that all the photographs depicted on this web page may be enlarged for more detailed viewing by moving your cursor to the photo and clicking on the image.
Four days after that inspection, on 6 May, an email arrived from another homeowner — this time in southwest Austin (78735), some nine miles from the first home mentioned above — with photos of a large brown recluse spider he’d found on a glueboard in an exercise room.
—Note that the geographical designations used in this article for the locations of these respective residences are slightly misleading. The first home mentioned above is described as being in south Austin, and the second as being in southwest Austin. In fact, though the first home lies (as the crow flies) about 7.1 miles south, it also lies 5.2 miles further to the west (the diagonal of that rectangle connects the two homes on a line about 9 miles long). This anomaly results from the fact that the Austin metro area is oriented along an axis running from the southwest to the northeast, and the area known as “south Austin” is generally agreed to apply to locations within the lower one third of that (where the first home is positioned); Austin’s middle third is customarily divided into western, central, and eastern sections; the second home falls in the western section, but is south of the Colorado River, and is therefore considered to be in “southwest Austin.” The diagonal straight line connecting both homes parallels the Interstate 35 corridor, a little more than ten miles to the southeast. Clear as mud, right?
That second brown recluse discovery resulted from a serendipitous event, the details of which bear repeating here:
Both couples are similar in age, with young children, and their families often spend time together. At one such function, the discovery of a brown recluse in the first family’s home came up in conversation. When asked what made the spider seem suspicious, the distinguishing features (a fiddle-shaped mark on the spider’s back, in combination with six eyes in three pairs on the head) were recited. Afterward, the second homeowner remembered seeing a conspicuous spider on a glueboard at his home. On examining that spider closely, he realized it was likely a brown recluse as well. The individuals involved in these two events are unusually observant people; both could easily have missed seeing the spiders in their homes, and even seeing them meant nothing until they took a closer look and realized they might be something other than ordinary arachnids. The lesson? Place a few glueboards around your home, in hidden, out-of-the-way places where they won’t be a bother, and look them over from time to time to find out what is living with you. You may be surprised at what you discover in the process.
One more thing before proceeding: The names of these homeowners have been withheld to protect their privacy. The precise locations of their homes are omitted from this narrative for the same reason, though zip codes — which give the reader a general idea of their respective locations — are provided.
Reports of brown recluse spiders in the Austin, Texas area are infrequent. In 2010 only one report from this area came in; in 2009 three reports were received, and in 2008, only one report — from a home in the Lake Travis area — was sent to me. In each of these previous cases save one, an inspection indicated that the brown recluse spiders involved were opportunistic invaders that were not present in large numbers. Monitoring, afterward, seemed to confirm that indication, as no additional brown recluse spiders were found.
The exception is a home in the city of Wimberley, Texas, on the southern edge of Austin, where a number of brown recluses have been found since my first inspection and application of non-toxic habitat modifiers. That particular home is unusual in that the interior walls are covered with a loose assemblage of lacquered knotty pine boards, which provide a multitude of cracks and crevices for spiders to hide in throughout the house; the home itself was built in the early years of the 20th century, and the arachnid fauna occupying the home’s interior and exterior is extensive and well established. Worse, the homeowner is a world-traveler who is often out of town, so a regular treatment with habitat modifiers — by the homeowner — is out of the question. She is amenable, however, to working out a plan of action for the future designed to bring her brown recluse infestation (the situation at her home would truly fit that description) to a halt…
The homeowner in southwest Austin wrote:
You were just out to my friend’s house to help him deal with the brown recluse his wife found under a bathroom sink. We had been discussing his situation over the last couple of days. Then, lo and behold, my wife spotted a spider on a sticky pad near her workout machine.
My friend seems convinced that it is, in fact, a brown recluse. And he, of course, recommended giving you a call.
Can you tell what it is from the photo? If it is one, we’d like to discuss having you come out to investigate. Thanks
He provided his telephone number in the message and soon we were discussing things on the phone. Not long after that we met at his residence, a spacious, upscale, two-story home in an affluent, gated neighborhood. Like his friend’s dwelling, this was an extremely neat and tidy, everything-in-its-place dwelling. The grounds, like the home’s interior, were immaculate, with a lush, diverse mix of botanicals that the lady of the household was very proud of. She, like me, prefers not to kill organisms without just cause, and uses bio-rational methods — including the regular application of mantises and other beneficial arthropods — to keep pests under control. Like my good friend Adette in Cedar Creek, when she sees a bug or spider inside her home, instead of killing it she shoos it out the door to live another day.
But she keeps a few glueboards in certain places in her home to prevent things from getting out of hand. We went to the glueboard with the brown recluse on it and took a look.
The largest spider on the glueboard was not only the largest spider on that glueboard, but it was also one of the largest, most robust brown recluse spiders I’d ever seen.
This specimen, like that of the first spider from south Austin, was a male, which made its size even more surprising. As with most spiders, brown recluse males are smaller than the females of the species, yet this specimen, while still within the range recorded for Loxosceles reclusa, was larger than the average female. The leg span, even with the legs partially curled up on the glueboard, exceeded 1.5 inches (40 mm), and the body, though shriveled up and bone dry (obviously a number of days postmortem) measured almost 1/2 inch (12 mm) from anterior head to posterior abdomen.
Loxosceles reclusa, like all other spiders, begins life very small and grows larger with every molt. Unlike most spiders, though, once the brown recluse attains adulthood (8-12 months after hatching) it tends to live a relatively long life that spans several (2-4) years, and under laboratory conditions, lifespans of as many as seven years have been recorded. The physiology of this spider is quite remarkable as well; it has one of the lowest heart and metabolic rates of the arachnids, rivaling those of the tarantulas and scorpions (Carrel & Heathcote, 1976), and under optimal conditions can live in a state of suspended animation for as much as a year, without food or water .
Because this home was so neat and clean, even a thorough search failed to find another brown recluse spider on this inspection visit. As with their friend’s home in south Austin, non-toxic habitat modifiers were sprayed in most of the dark corners and recesses of closets and rooms, behind and under furniture, and in the garage, in the downstairs portion of the home. The homeowners were shown how to apply the habitat modifiers (a quantity of which was provided) themselves, and weekly applications were suggested for the coming six weeks. Sticky monitoring traps were provided, with suggestions that they place them out after a few weeks, to monitor the arthropods that were living in their home. That would allow me, on the next visit, to quickly determine how to best formulate an on-going PestAvoidance program tailored specifically for their situation.
Back at the lab, the fauna on the glueboard was examined to see if any of the other adult spiders it held were recluse spiders. No adult recluses, beyond the large one previously noted, were found, and an email was sent to the homeowner with that observation duly noted, along with my hope that this spider was merely an opportunistic invader from the outdoors. Two months later, however, the glueboard was analyzed again, this time under higher power magnification to determine the identity of the microscopic fauna it held. To my surprise, four of the minute organisms on the board were discovered to be tiny, juvenile recluse spiders. The exact locations of these spiders are annotated on the edge of fig. 100, above. Figures 105 through 113 show the habitus (general appearance) and dorsal heads of each of these juveniles.
Obviously, the large male recluse was not an opportunistic invader from outdoors. Rather, a female (not yet observed) had produced eggs, hatched young, and was likely living inside the home, probably not far from where the glueboard had been reposing when these spiders stumbled upon it.
It was time for another visit to this site anyway, so an email was sent out to the homeowner detailing my recent discovery, and asking if he had noted any brown recluse sightings.
He replied within a few hours, informing me that yes, by coincidence he had recently found two recluse spiders on glueboards at the doorway from the home into the garage (these were thrown away, and could not be examined, but are designated as BRS 78735#6nc and BRS 78735#7nc for reference purposes), and — just the night before — had killed a brown recluse in his game room (BRS 78735#8).
Some specialized equipment involved in his work had recently been brought into the garage and game room from a storage facility several miles distant, and he suspected the spiders were hitchhikers from that locale, because he had not otherwise seen any recluse spiders since my first visit.
For reasons that need not be explained here, a very narrow window of opportunity existed — that very afternoon only — to carry out another inspection and application of habitat modifiers. Placing my other appointments on hold was not a problem, and it was possible to travel to the home immediately.
This time the entire home was inspected again, without finding any live recluse spiders, but noting the presence of at least two theridiid cob webs, and what appeared to be cribellate-like hackle webs that might have been produced by recluse spiders.
Following the inspection, the home was treated with non-toxic habitat modifiers, upstairs and down.A tentative appointment was made for a date one week hence, to repeat this application.
The spider killed the night before — BRS 78735#8 — which, like the first spider found here, happened to be a male, was collected (the homeowner had kept for me in a napkin), preserved in 70% ethanol, and taken to the lab for analysis. As figures 208-210 show, the characters of the male palp are wholly consistent withg those of Loxosceles reclusa.
- 12 July 2011: A follow-up call was made to the homeowner at 78739 on 12 July 2011. About three weeks after my visit of 2 May 2011 a dead brown recluse (BRS 78739#2nc) was found in the same bathroom where the first spider had been observed on 29 April. Later, about a week ago, a live brown recluse (BRS 78739#3nc) was found in the kitchen, on the countertop, in the mid-afternoon. That spider was hiding under a cloth towel or a paper bag, and was immediately killed. Neither was preserved, and so are not available for analysis. The homeowner reported that he was having difficulties keeping the glueboards intact, as his young children would find them and, well… bye, bye glueboard. Those that escaped (primarily in the garage) had not trapped any brown recluse spiders, though. Glueboards are notoriously vulnerable to the machinations of small children, and R&D is underway at EntomoBiotics Inc. to produce a workable child-resistant device that can be used to monitor nocturnal thigmophilic arthropods, like brown recluse spiders and scorpions, without disrupting things for the children and adult humans who also live there. This homeowner has fallen behind on the weekly applications of habitat modifiers we had discussed on my first visit, which explains why the BRS are still being seen. It is understandably difficult for homeowners to follow the regular, weekly applications required to mount a successful PestAvoidance program against BRS, because homeowners have enough on their plates as it is. That’s why I recommend carrying out a full PestAvoidance application program, starting with a series of weekly applications, then by several semi-monthly applications, followed by monthly applications until — generally by the end of twelve full months — the BRS infestation is fully controlled.
- Carrel, James E., and R.D. Heathcote, 1976. Heart Rate in Spiders: Influence of Body Size and Foraging Energetics. Science, 193: 148-150.
- Cramer, Kenneth L., 2008. Are Brown Recluse Spiders, Loxosceles reclusa (Araneae, Sicariidae) scavengers? The influence of predator satiation, prey size, and prey quality. J. Arachnology 36:140-144.
- Cramer, Kenneth L., Alex V. Maywright, 2008. Cold temperature tolerance and distribution of the brown recluse spider Loxosceles reclusa (Araneae, Sicariidae) in Illinois. J. Arachnology 36:136-139.
- Gertsch, Willis J., 1958. The Spider Genus Loxosceles in North America, Central America, and the West Indies. AMNH Novitates 1907: 1-46.
- Gertsch, Willis J., 1979. American Spiders, 2nd Edition. Von Nostrand Reinhold Company.
- Gertsch, Willis J., Franklin Ennik, 1983. The Spider Genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bull. AMNH 175: 254-360.
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- Hite, J.M., W.J. Gladney, J.L. Lancaster & W.H. Whitcomb, 1966. The biology of the brown recluse spider. University of Arkansas, Fayetteville. Agricultural Experiment Station Bulletin No. 711.
- Hogan, Christopher J., Katie C. Barbaro, Ken Winkel, 2004. Loxoscelism: Old Obstacles, New Directions. J. Annemergmed 08: 608-624.
- Parks, Jennifer, William V. Stoecker, Charles Kristensen, 2006. Observations on Loxosceles reclusa (Araneae, Sicariidae) feeding on short-horned grasshoppers. J. Arachnology 34:221-226.
- Sandidge, Jamél S., 2009. Brown Recluse Spiders: A knowledge based guide to control and elimination. Pubkished by BRS Pest Control, McLouth, KS.
- Ubick, D., P. Paquin, P.E. Cusing and V. Roth, editors, 2005. Spiders of North America. Published by the American Arachnological Society.
- Vetter, Richard S., 2008. Spiders of the genus Loxosceles (Araneae, Sicariidae): a review of biological, medical and psychological aspects regarding envenomation. J. Arachnology 36:150-163.
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