An Invasion of Striped Bark Scorpions at a Residence in Cedar Creek, Texas 4

— This article by Jerry Cates, first published on 19 June 2010, and last revised on 24 April 2016, is the basis for a televised episode featured in the 2012 Animal Planet TV series INFESTED. © Bugsinthenews Vol. 11:06(04).


Striped Bark Scorpion (Centruroides vittatus), fluorescing on wood flooring; Cedar Creek, Texas--06.17.10

Striped Bark Scorpion (Centruroides vittatus), illuminated with ultraviolet light.

General Information on Striped Bark Scorpions:

Early in 2009, the new owners of a residential home in the deep woods of Cedar Creek, Texas, asked me to identify to species the snake that had shed its skin inside their new home. They had just closed on the property, a large one-story dwelling, with a huge, floored attic, on 30 acres of thickly forested ranch land. The land was part of an 1827 land grant by the Mexican government to Stephen F. Austin, and had been owned by close relatives of the Austin family until David and Adette bought it.

On their first visit after closing they’d found a snake skin, but not the snake itself, in the home’s laundry room. Might the ophidian trespasser still be inside the home? they asked. Could an examination of the snake’s old skin shed light on the species of snake involved?

The answer to the first question was “Not likely,” and to the second, “Probably.” Examining the scale pattern of the head (the shed skin of the head was intact), counting the scales at mid-body, checking the morphology of the anal scale, and noting the division of subcaudal scales beyond the vent, established that this had come from a harmless colubrid rat snake. It had probably entered the house in search of something to eat. Except for a multitude of scorpion and spider carcasses, none of the rodent prey favored by colubrid rat snakes was in evidence — the usual evidence being rat and mouse “pellets,” which we did not find. There was no basis for believing the snake would have remained inside the home.


— Note: Snakes almost never infest the interiors of homes. Their rare incursions there are usually brief and transitory. Many Texas ranchers take advantage of this characteristic; when they discover rats or mice in their homes, they go down to a nearby barn, root around in the loft until they find a mature rat snake, then haul it over to the house and toss it into the attic. They know from experience that — once the rat snake succeeds in decimating the rodent population there — it will soon slither, unseen and unheard, back to the barn “where it belongs.” Snakes, like all other animals, only loiter where they find the triple combination of prey, mates, and favorable habitat. Thus the rancher rarely if ever sees that snake inside the ranch house. Unless, that is, a mouse or rat problem develops again, in which case the rodents produce scent trails that snakes may follow into the home…


Since that first visit in 2009, it has been my pleasure to get to know David and Adette, the owners of the ranch in Cedar Creek, quite well. They are wonderful people who love animals and children. As owners of The Chuckling Hound Pet Ranch, they rescue stray and sick dogs, nursing them back to health in their spacious, well-kept kennels. Then they diligently find the revitalized canines good homes, with loving families. Adette also has a thriving pet-sitting business. David — like my brother Allen (who has since published a book, Honor Denied: The Truth about Air America and the CIA) — is a veteran U.S. Marine Corps pilot with battlefield experience. Today he works as a financial advisor, and serves as a dedicated basketball coach with a large, nearby independent school district.

When you look into the eyes of this couple, you can’t help but see the spark of high intelligence, and feel the fire of determination. They are not ordinary people. Not by a long shot. They’re certainly not the sort to let adversity get the better of them.

As mentioned earlier, the initial focus of my first trip was a snake skin. Like most people, David and Adette harbored an almost primal disgust of such animals, and the very idea of sharing their home and yard with serpents — even a “good” rat snake — was simply unacceptable.

But snakes were only part of the picture. It was clear that a large number of scorpions and spiders also resided inside their new home. The structure, though “new” to David and Adette, was over twenty years old, and had lain vacant for some time. On that first visit the floor of every room was littered with the carcasses of dead scorpions. The carcasses of dead spiders, too, were relatively abundant. Naturally, we discussed the obvious need to deal with them. It happened, however, that they had already made arrangements with a nationwide pest management company to have the home and yard sprayed with pesticides, expecting that would quickly resolve whatever infestations might be involved.


— Note: A number of traditional and advanced pesticides are labeled for spider and scorpion control today. Most university entomology departments and state-funded agricultural extension agencies provide technical advice, via Internet articles and other media, on methods and pesticides for scorpion control and eradication. In addition, most professional pest management companies offer scorpion control services, and many mention — in connection with those services — how their research has identified “the best pesticides for the job.” The public views these sources as having the stamp of authority, and assumes that scorpion control using pesticides is a snap for licensed exterminators. To the credit of many universities, extension agencies, and pest management companies, the technical articles they publish mention, somewhere in their texts, that pesticidal control of scorpions is difficult if not impossible, and should never be attempted as the sole means of control.


Though my initial involvement was limited to helping David and Adette avoid future snake encounters, curiosity led me to conduct a quick survey of what appeared to be a burgeoning scorpion infestation. Along the way, a few of the dead spiders scattered through the house were examined using a portable microscope I had brought along. Many of the latter turned out to be spitting spiders, not the feared brown recluse they had thought them to be. Since the six species of spitting spiders found in Texas are harmless to humans, they were nothing to worry about. The scorpions, as expected, were striped bark scorpions (Centruroides vittatus), the most common of the 18 scorpion species native to Texas.

Notice the photo above, and the one below it, which depict two of the scorpions found after dark on a later visit to this ranch, in June, 2010. When bathed in ultraviolet (UV) light, scorpions glow a bright lime-green, making them stick out like a sore thumb.

A colony of these scorpions, collected at this site, was later studied at the EntomoBiotics Inc. lab, some thirty miles northwest, in Round Rock, Texas. Ordinarily one would not use the words “colony” and “scorpions” in the same sentence, as many of the approximately 1,200 species of scorpions presently recognized worldwide are anything but sociable creatures. With some scorpion species, cannibalism is routine (Polis et al., 1979). Cannibalism — which in many species of scorpions tends to occur (1) intentionally in conjunction with the mating ritual or (2) unintentionally when a foraging scorpion mistaking one of its own kind for prey and thereupon kills and eats the hapless victim of its errant judgement — does not occur nearly as often with the striped bark scorpion. At least one study (Yamashita, 2004) indicated that cannibalism provided 9.3% of this scorpion’s diet, presumably as a result of mistaken identification.

Studies at the EntomoBiotics lab indicated that predation of young, recently born scorpions by adults, especially under conditions of food deprivation, is common with this species. Authorities on scorpion behavior have determined that adult males are the primary offenders in this regard, but such behavior is not typical under conditions where food is abundant and populations of scorpions are relatively low and dispersed.

The gregarious nature of this species has significant implications regarding its foraging and aggregation behavior. These scorpions tend to get along well with their own kind, and even gather in large numbers, often stacked one atop another, amicably sharing the available space in their habitations. Even when food is withheld for several weeks, they continue to live together in harmony. This behavior helps explain why the species is capable of causing serious pest issues around homes and businesses in their range when conditions favoring high population densities are present.

It is convenient that scorpions fluoresce under UV lighting, as that makes them easy to spot after dark when searching with a UV light source.


NOTE: As you examine the UV images depicted on this web page, especially if you click on them and view the enlarged images, you will notice they are slightly out of focus. The autofocus firmware of most cameras, whether analog or digital, is optimized for light in the visible spectrum. This prevents the camera from focusing properly on objects illuminated by UV light. The remaining images in this post are illuminated with visible light.

— A Word of Caution: If you use UV lighting to find scorpions inside a home or yard, follow the  lighting manufacturer’s instructions carefully, and ALWAYS wear protective eye-wear fitted with approved yellow UV filters to avoid eye injury. UV light can be very harmful to the human eye if used improperly.


Striped Bark Scorpion (Centruroides vittatus), fluorescing in native vegetation; Cedar Creek, Texas--06.17.10

Striped Bark Scorpion (Centruroides vittatus), fluorescing in native vegetation; Cedar Creek, Texas–06.17.10

In the year following my first meeting with David and Adette in early 2009, they went through what can only be described as an excruciating ordeal. The sheer number of live scorpions they found running around inside their home every day was unbelievable.

Worse, using pesticides to control scorpions is a dicey, unsatisfying project, as they and their exterminator soon discovered. Alternative methods, particularly natural ones involving mechanical habitat modifications supplemented with natural plant oil sprays and granules, have to be used extensively, and methodically, with serious infestations like this one, and most homeowners are reluctant to do that right off the bat.


Note: Shortly after an account of this scorpion infestation was posted on BugsInTheNews, a producer with Darlow Smithson Productions, creators of the Animal Planet TV series contacted me for permission to document it on film for one of their upcoming episodes. Client privacy is important, and my guess was David and Adette would refuse the invitation to be portrayed publicly on television. To my surprise, they agreed without a moment’s hesitation. Videotaping took place in the summer of 2011.

The episode, Hostile Takeovers, was partially narrated by Jeffrey White, a New Jersey research entomologist. Jeff admits he knew almost nothing about scorpions before being assigned to work with this episode, and had to cram to prepare for his involvement.

The episode first aired in the U.S. on January 20, 2012. Although certain facts were left out and the sequence of events was altered to heighten the drama, the essence of David and Adette’s experience, and of my interaction with them, was reasonably accurate — with a few important caveats.

For a number of reasons, the episode makes no mention of the first 12 months after David and Adette moved into the home. During that period a nationwide pest management firm treated their home and yard for scorpions without making a noticeable dent in the scorpion population. The televised version portrays David carrying out the pest management project strictly on his own, using nothing but bug bombs, then reports that, when the use of traditional pesticides (“chemical warfare,” as they put it) didn’t work, I was called in for consultation.

Although I supplied David and Adette with natural plant oil habitat modifiers, in the form of liquid sprays and granules, I did not apply them in the attic as the episode reports, but merely demonstrated how to properly use them there, throughout the home, and in the yard. These are used, not as pesticides, repellents, or pest mitigants, but as non-toxic habitat modifiers that produce an environment that neither attract nor nurture scorpions and their prey.

The misconception that scorpions are warehoused inside portions of residential homes with solid exterior walls (like those of David and Adette’s home, in contrast with homes having exterior clapboard, vinyl or aluminum siding walls with numerous cracks and crevices where scorpions can, and often do, hide during the day) is so prevalent that it was presented as fact in the Animal Planet episode. The episode perpetuates this myth in a powerful way by having their entomologist consultant, Jeff White, opine that spraying the attic with plant oils would drive them out of the attic, into the living areas of the home.

This is based on three presumptions: (1) that natural plant oils repel pests, (2) that large numbers of scorpions are likely to congregate for long periods inside a hot, dry, attic, and (3) that scorpions only showed up in the living area of David and Adette’s home sporadically.

My work at this site, and my understanding of scorpion biology, specifically that of the species Centruroides vittatus, provides strong evidence that all three of these presumptions are wrong.

This scorpion prefers to spend the daytime hours in moist, cool refugia, quite unlike the environment of a hot, dry attic that approximates an oven in the summertime. All scorpions are nocturnal. The ones that plagued David and Adette almost certainly entered their then-cool attic at night, from the roof, after accidentally falling from overhanging tree limbs. When the sun began to heat the attic in the daytime, the scorpions would naturally migrate to its coolest portions. It appeared they would first migrate to the attic’s center where, attracted by the pheromones of the scorpions that had come before them, they’d slip into the confines of a laminated wooden beam. There their thigmophilic natures would give them temporary refuge as they waited for nightfall, as long as temperatures didn’t increase too much.

As temperatures continued to soar during the day, these scorpions, which exhibit a strong sensitivity to signs that their bodies are becoming dehydrated, would be forced out of the now-inhospitably-hot laminated beam into the cooler, darkened wall voids of the living area below. There, too sensitive to light to leave the wall voids in the daytime, they would await the opportunity, when darkness fell, to escape to the outside yard.

Accordingly, the attic and the living areas of David and Adette’s home served merely as way-stations for the scorpions to pass through on their way from the roof — where they’d fallen by accident — back to the yard and its myriad of ground-level, cool and moist hiding places that served as their natural, preferred habitat.

I estimate the time period for this transit, during the summertime, at less than 24 hours on average. Of course, some scorpions might accidentally migrate back to the attic when it cooled off, only to be forced out again the next day. Thus, some might take 48 to 72 hours to complete the trip back to the yard. A study at the EntomoBiotics Inc. laboratory, designed to test this hypothesis, is planned for the near future.

In the televised episode, the entomologist that David and Adette called out (a stunt double playing me, but portrayed as squirting liquids throughout the attic from three different kinds of spray bottles, his face comically contorted as though in fear of being stung) treated only the attic with “his natural plant oils.”  Afterward, according to the Animal Planet story line, the scorpion numbers inside the living areas of the home diminished immediately. Then, several days later and without any warning, they began showing up in larger numbers than before, inside the kitchen. Jeff White then explains to the TV audience how spraying the attic with the plant oils would naturally disperse them, from that location, to the rest of the home.

This contrived scenario suffers from several difficulties, as already pointed out. On the surface, though, it seems to make sense. Thus it contributed to the drama, as intended.

Natural intuition suggests plant oils would repel scorpions. We are taught, for example, that the oils in plants like rosemary are natural repellents that insects, spiders, and other organisms avoid like the plague. Thus, spraying the attic with similar oils would force any scorpions exposed to the spray to flee from the attic to the living quarters, where they would show up in larger numbers than before. But intuition is often wrong, and in this case it is. This is not a criticism of Jeff, as it is easy — even for an experienced entomologist — to make a mistake of this nature.

Over the past several years, my research in this field, and the long list of even worse mistakes that I’ve made in the process, have taught me to distrust hypotheses based on intuition without first ensuring they are consistent with all that can be learned about the organism involved. A similar process, for example, led me away from the intuitive need to spray broadband pesticides to the counter-intuitive notion that the natural predators of puss caterpillars are far more effective when allowed to do their job.

In the case before us, it is the scorpion’s unusual sensory organs, the pectines (a pair of ventral sensory brushes that the scorpion uses to “sniff” the chemical cues in its environment), that must be taken into account. Scorpions rely on these organs to find prey and mates, but their pectines only function in habitats that are relatively free of extraneous volatile chemicals. In such an environment the pectines send signals to the scorpion’s brain that allow it to efficiently discriminate between a variety of pheromones and other chemical signals laid down by other scorpions, and by the insects they prey upon. When in the presence of a flurry of extraneous chemical signals, the pectines send such a multitude of signals that sorting them out becomes impossible. In such an environment, the pectines become useless.

Without its pectines, a scorpion is essentially blind (literally so, since their primitive eyes are not used to find prey or mates). In this state the scorpion does not move anywhere quickly, and its movements — in whatever direction it takes — are anything but predictable or coordinated. The movements of the scorpions at David and Adette’s home, however, were both. They entered the attic from the roof, loitered there for a few hours before being forced by heat and lack of water into the voids of the walls downstairs, and as soon as night fell they scampered back outside as fast as possible.

In my interview with the Animal Planet producer, I explained that the scorpions in the attic did appear to be drawn to the centralized laminated beam. My research showed that they used this beam as a temporary refuge (depositing small amounts of pheromones while there) on their way back to the yard by way of the wall voids on the ground floor. I explained they were not warehoused in the attic, and thus did not remain in the attic very long, even without the application of plant oil sprays.

However, once that beam was made attractant neutral by the cleansing action of the plant oil sprays (by washing away the pheromones left behind by the scorpions that had loitered there earlier), newly arriving scorpions stopped congregating at that location, even temporarily. Few if any outside scorpions would be expected to enter the attic from the roof once the plant oils were applied regularly. Every scorpion that fell on the roof in the nighttime had two choices: slip into the attic, or stay outside and amble down an exterior wall to the ground.

In the past, most that landed on the roof probably entered the attic because it offered a dark safe haven replete with promising pheromone trails, and though warmer than the exterior, was relatively cool during the nighttime. Despite being repelled by the higher temperatures, the scorpions would have been sufficiently enticed by the pheromone trails to disregard the temperature disparity and proceed into the attic. Once the plant oils were applied, the subtle pheromone trails would be masked, and the scorpions that entered would sense the loss of their ability to navigate with their pectines. Given the choice of (1) entering an attic where their pectines would immediately show signs of malfunctioning, or (2) staying outside where pectine navigation would continue to function normally, most if not all the scorpions on the roof would naturally choose the latter by — in a ho-hum sort of way — taking a pass on the “opportunity” to enter what amounted to an unpromising attic.

It’s like when one human wants to carry on a quiet conversation with another human at a well-attended cocktail party, but the room they are in has too many people speaking at once and ordinary speech cannot be heard above the din. If the conversation is important and private, and optional places to converse are available, the two are likely to migrate to a quieter room where the noise lets their private conversation proceed. They aren’t necessarily repelled by the noise. In fact, lots of noise is comforting to humans and scorpions alike under the right circumstances, such as when each congregates together in large numbers.

Humans happily congregate with regularity in restaurants, nightclubs, and bars. Striped bark scorpions tend to congregate in their communal refugia, where they clump together in heaps of ten to fifteen scorpions crammed on top of one another. In such places the pheromone noise, picked up by their pectines, is deafening, yet when prodded with a forceps, such clumps of scorpions don’t scatter but — instead — tend to squeeze even more tightly together, suggesting that all the members of the clump take pleasure and feel a sense of safety within their communal aggregation.

As with human congregations, noise is welcomed when it is non-threatening and when “chilling-out” in the company of others is desirable. By contrast, when looking for a mate or searching for food, humans and scorpions alike are attracted to quieter places where the senses can be tuned and the search can be carried out carefully and methodically.

In summary, excess sensory noise is not a problem in a communal, perceptually safe setting, but is distracting to individual scorpions who are in “foraging mode,” away from their communal nests in yards and forests. The plant oils in David and Adette’s attic make the beam, where it was applied freely, and the attic in general, where it and the aromatic plant oil granules, were applied lightly throughout, attractant neutral and unnavigable. By comparison, because the outside walls of the home remain attractant-positive and highly navigable, the scorpions would forsake the warmer attic for the coolerexterior walls as a means of returning to the yard below.

David did inform me that, the night after he sprayed the beam the first time, he noticed one scorpion on the wall, downstairs, near where the beam was located. It appeared disoriented, consistent with the effects of having its pectines deactivated. Still, that sighting was not extraordinary. Scorpions were already being seen in the living quarters of the home on a regular basis, as they had since David and Adette first moved in, some 18 months earlier. Aggressive applications of habitat modifiers (the natural plant oils and granules), simultaneously in the attic and in the living quarters, led to an immediate reduction in sightings in both areas. A short time afterward the scorpion sightings diminished to zero.

The non-toxic oils and granules I supplied David and Adette worked best if applied, throughout the home, at least once a week until the scorpion invasion was brought under control. Thereafter once a month would suffice during the warm months of the year. For many if not most home and business owners, calling an exterminator out that often to apply non-toxic habitat modifiers made no sense when they could do it themselves for a fraction of the cost.

From the start, David and Adette conducted the project strictly as a do-it-yourself operation. Initially, they were reluctant to carry out a truly thorough application of the oils, inside the home. As David mentions in the TV episode, it made the house smell like “one huge cedar chip.” The original formula had a relatively robust odor profile that can wear thin. We’ve since developed a low-odor formula for home interiors, that cleanses and neutralizes pet and invertebrate odors about as well as the stronger-smelling original formula. We’ve since used it with success in a number of home interiors, without making the house smell like a miniature Amazonian botanical garden.

Once David and Adette committed to an aggressive, thorough, and consistent application of the non-toxic botanical-based oils inside the home, and of granules impregnated with the same family of plant oils in the floor of the attic and in the yard around the home, the scorpion invasion ground to a halt. This fact the TV episode makes clear.

At the end of the televised episode, David and Adette are portrayed celebrating, over a glass of wine, the realization that their home is now scorpion free.  As a footnote Adette, with a genuine look of concern on her face, says “I’m confident there’s been a huge decrease, but I’m not confident the scorpions are gone…”

She’s right, of course.

Controlling scorpions in a home or yard is not an event, but a process. That’s true regardless of the method used to achieve control, including methods and materials associated with habitat modification techniques. Besides regularly applying the natural oil sprays and granules, tree limbs extending over the house need to be trimmed, and brush and debris must be cleared from the yard. In short, David and Adette cannot let their guard down, but must continue to maintain an environment that is free of harborage where scorpions can hide and breed. In the deep woods of Cedar Creek, and other locales where scorpion populations are endemic, habitat modification is a never-ending process that must be renewed, month to month, and year after year.

Fortunately, keeping the scorpions out of David and Adette’s yard and home was accomplished using non-toxic, non-pesticidal, non-repellent methods and products. Using pesticides didn’t work, as their experience and the valiant efforts of the professional pest management firm that did all they could to make them work, proved. As long as David and Adette keep up their part of the bargain, by practicing good habitat modification techniques consistently, they will enjoy a perpetually scorpion-free environment.


Though David and Adette are philosophically opposed to using poisons (Adette never kills a spider; she shoos it out the door to live another day), the extreme nature of this scorpion infestation drove them to consult with professional pest management companies who were specifically wedded to the belief that “good” pest management and powerful pesticides go together.

They already knew, from other articles they’d read in BugsInTheNews, that reliance on pesticides, as the first line of defense against pest infestations, wasn’t the focus at EntomoBiotics Inc. This company’s emphasis, since 1980, has been to resolve pest problems naturally, without pesticides — and without killing pests — whenever possible. That practice relies on PestAvoidance, using habitat modification techniques and products. If pests can be “managed” without toxicants, that’s what makes the personnel at EntomoBiotics Inc. smile.

Habitat modification is crucial to PestAvoidance. It starts with mechanical modifications of the environment to reduce the number and variety of habitats that can be exploited by pests. Next, whatever habitats remain must be rendered attractant and nurturant neutral, using non-toxic, non-pesticidal, non-repellent materials that don’t even qualify as pest mitigants. Limiting the scope of treatment to such materials avoids the production of pesticide-resistant pests.

Our focus on habitat modification led to the development, for our use and for our clients to use as well, of several liquid sprays and mulches made from natural plant oils and their derivatives. The idea was to produce environments inside homes, and outside, in and around residential and commercial yards, that don’t attract or nurture pests. Within such environments, pests don’t stick around, not because they are repelled or killed, but simply because, as far as they can tell, there just isn’t anything there to make them “want” to stick around.

David and Adette liked the PestAvoidance approach, especially for “the long run.” Like most, though, using habitat modifier sprays and granules didn’t sound very useful for “the short term,” when the joy of killing the scorpions outright was uppermost in their mind. Yes, joy is the word. The scorpions made them angry. Angry enough to want to retaliate. PestAvoidance doesn’t do that. Instead, it’s like saying to the scorpions “Look, we respect your right to exist, just don’t do it here.”


FACT: Convincing the scorpions to move is, in all honesty, much better than killing them. Like it or not, we’re better off because of the huge numbers of insects they kill, nightly, in the forests and grasslands around us. Furthermore, when habitat modifiers are used to get the message across that there isn’t anything “here” worth staying around for, the scorpions take the hint, right away, and move along.


But it’s a counterintuitive idea, contrary to accepted wisdom, and most people are not prepared to believe it. It was no surprise that David and Adette reacted like most people until they could see, for themselves, how well it worked.

The first habitat modification recommendations passed on to David and Adette were for them to remove the vines that covered one side of the house, and to trim the tree limbs stretching over their roof. Vines harbor scorpions and their insect prey, and striped bark scorpions love to ply the uppermost reaches of trees at night, searching for prey. On finding an insect to eat, they’ll fall out of the trees, onto the roof, with the insect clasped in their pincers. Later, to get to the ground, they first enter the attic, or the vines, and work their way to the ground See the problem?

Next the brush, wood piles, and other debris in their extensive yard — every possible haven for scorpions — had to go. Getting that done would be laborious work. Lots of it.

But while David and Adette had plans to do all those things, they couldn’t do much in a couple of days or even a couple of weeks. And they needed these scorpions wiped out pronto.

As mentioned above, an Internet search on scorpion control immediately produces a huge list of experts in academia, state-sponsored agencies, and the pest management industry, testifying that scorpion control, carried out by licensed professionals using traditional pesticides is a snap. Under the circumstances, who could blame David and Adette for focusing on that approach? They took the bait, making arrangements with a firm having over 100 years of experience, thousands of well-trained technicians worldwide, and indisputable expertise at wielding the most advanced pesticides in the business.

That company’s technicians came out and doused David and Adette’s home and yard with a select recipe of pesticides specifically labeled for scorpions, promising a quick resolution to their scorpion infestation. In addition, David and Adette also began the slow process of making mechanical habitat modifications while, albeit half-heartedly, applying the habitat modifier spray and granules I supplied inside their home and around its perimeter. My recommendation that they do this aggressively seemed, under the circumstances, a bit overblown, given that another company was spraying magically powerful pesticidal toxicants that would take care of the problem in the blink of an eye.

Striped Bark Scorpion (Centruroides vittatus), dorsal body; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), dorsal body; Cedar Creek, Texas–06.18.10

PestAvoidance is the Rodney Dangerfield of the pest management industry. Never mind that it is truly an advanced form of Integrated Pest Management (IPM); it still gets no respect. Neither does IPM. Though that concept has been around for a long time, it has never garnered much acclaim in the real world.

Perhaps the cause lies in the historical inability of proponents of IPM and PestAvoidance to articulate — in brief, easily understood terms — how those methods provide a fully-effective alternative to conventional pest management. It isn’t easy to explain.

Attention wanes as complexity increases. As long as John Q. Public believes that the KISS (Keep It Simple Stupid) principle rules in all things, IPM and PestAvoidance will not elicit a great deal of interest. IPM and PestAvoidance are anything but simple. But, like Occam’s Razor, KISS isn’t always the best way to deal with complex problems.

In the past and today as well, both IPM and PestAvoidance are mistakenly viewed as weak-kneed and over-complicated stepsisters to “demonstrably effective” conventional pest control. Outside the very few — like EntomoBiotics Inc. — who champion them, almost nobody believes they offer legitimate, full-fledged solutions to truly serious pest problems. Oh, most agree they’re fine as “feel-good” solutions to non-existent pest problems, but they’re worthless against “real” pests. At least that’s what most people think. Conventional wisdom has it that it’s politically correct to give them generous amounts of lip-service, but it’s impossible to achieve anything good by using them, especially under situations where genuine pest problems exist that need to be dealt with decisively and quickly.

Never mind that such views are just plain wrong. Our work, even as early as 1980, focused on applying IPM methods consistently (PestAvoidance didn’t exist back then), wherever possible, and it was amazing — from the very start — how well those methods worked.

Admittedly, they couldn’t be used everywhere. Sometimes conventional pest management products and methods are absolutely necessary. Sometimes: like with fire ants in nursing home and hospital grounds, and termites infesting dwellings on wooden pier and beam foundations, among other examples. But most of the time PestAvoidance techniques work best of all, even for acute and chronic pest situations. And, yes, even for — actually, especially for — scorpions.

Striped Bark Scorpion (Centruroides vittatus), frontal; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), frontal; Cedar Creek, Texas–06.18.10

Not only that, but PestAvoidance provides a unifying concept that makes it easier to understand why IPM is so worthwhile.

The key to IPM and PestAvoidance is habitat modification, directed at reducing harborage and either removing or neutralizing ordinary environmental attractants. It is natural to want to introduce something foreign, like toxic pesticides that kill in large numbers, but — almost without exception — such pesticides usually do more harm than good.

If “body count” is the primary object, broad-band pesticides are definitely the way to go. But among the bodies of the pests that such pesticides kill will be found the bodies of non-target, non-pest organisms that are killed along with them. These non-pest organisms were probably doing their best to keep the genuine pests under control. In most ecosystems the beneficial organisms there do a much better job of pest control than any of the pesticides on the market.

It is common to question why we should worry about that. My research on the puss caterpillar — which has the most painful, long-lasting sting of any lepidopteran larva on the planet — provides just one example of how important it is to keep the beneficial organisms in our midst alive. Someday, wghen you have some spare time, read the results of that research posted at the links provided immediately below:


Links:   (1) Puss Caterpillar General Information.    (2) The Puss Caterpillar’s Stinging Apparatus. (3)Puss Caterpillar Extermination. (4) The Puss Caterpillar’s Natural Predators. (5). Puss Caterpillar Stings–Medical Interventions. (6) Puss Caterpillar Stings–Home Remedy First Aid Measures.


Striped Bark Scorpion (Centruroides vittatus), lateral; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), lateral; Cedar Creek, Texas–06.18.10

Because it is not extermination, PestAvoidance does not use pesticides, repellents, or pest mitigants. Instead, if anything beyond mechanical habitat modifications are needed — and surprisingly often that is enough — it uses non-toxic habitat modifiers, most of them naturally derived from essential plant oils, that in the concentrations recommended are not harmful to the target pests.

But why on earth would we not want to kill or harm scorpions? Jan Beccaloni, curator of Arachnida and Myriapoda at the Natural History Museum in London, writes about the beneficial contributions scorpions make to the ecosystems they inhabit in her 2009 book Arachnids. Scorpions, though feared and even hated, are beneficial insectivores that keep insect populations down in the areas where they are found.

Most of the time, the scorpion population in any given locale is so small that you have to hunt hard to find one. The only reason that David and Adette’s home and yard were infested with these arachnids is that they were finding abundant insect prey to feed on.

It wasn’t anybody’s fault, it just happened to be the case.

Absent all that prey, those scorpions would migrate to other parts of the forest, where food was more plentiful, or their populations would drop to the levels typical for ordinary ecosystems, levels at which they pose almost zero risk to the humans living nearby. The other side of the equation, which was largely invisible to David and Adette, was the huge number of insects these scorpions were removing from their trees and yard every day. In other words, the scorpions at David and Adette’s ranch were actually doing them a huge favor, even if the nature of that favor was essentially invisible to them.

Literally tons of katydids, grasshoppers, wood roaches, beetles, and the like, were being eaten by the scorpions each night. One night in 2010 the three of us — myself, David, and Adette — walked about their yard amidst an overpowering cacophony of tree insects. The sound was so powerful we could not talk over the din without shouting. Why were those insects there? Didn’t they need to be dealt with, too? If the scorpions were all killed off, what would happen next? The answer is well known to ecologists. Whenever a strong natural predator is removed from an environment, its prey proliferates to amazing multitudes that are capable of wreaking unimaginable havoc, often overnight.

PestAvoidance isn’t like that. Instead of exterminating pests it resolves the negative issues they represent by creating a limited ecosystem — for example, a home and the yard around it — that does not nurture them or their prey. As a result, both sets of organisms migrate elsewhere, to locales where they can feed on each other without creating nightmares for the humans who live nearby. Though from a visceral perspective this approach is less satisfying than exterminating the scorpions outright, it is recommended because it is less expensive, more effective, and longer lasting.

An important part of the habitat-modification process involves removing attractants — things that draw the target pest or pests — from the area, making that area attractrant-neutral.

That can be accomplished merely by introducing low concentrations of essential plant oils that wash away, clean up, and effectively neutralize attractant pheromones and prey odors. Pests that constantly scan their environment for such things are not vectored to and within the area by them. Such habitat modifications are, in most cases, sufficient to cause the target organisms to go elsewhere and avoid the habitat-modified, attractant-neutral ecosystems they encounter, where tracking prey and mates is difficult or impossible.

Striped Bark Scorpion (Centruroides vittatus), laterofrontal; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), laterofrontal; Cedar Creek, Texas–06.18.10

As mentioned earlier, David and Adette had already contracted with a nationwide pest management service that uses the most advanced toxic methods available to the pest management industry. Their object was to actually kill the scorpions in the yard, in the living areas of the home, and in the attic.

The service technician for that company drove up to the house right as my departure, at the end my first visit in 2009, was imminent. We waved at each other in a mutually friendly gesture that was genuine. Remember, we’re both members of the same industry, and even if we take different approaches to solve pest problems, we respect one another. My relationships with other technicians and certified applicators is not only cordial but strong and enduring. We’re not adversaries, but cooperators. It is right to salute the work of all those dedicated to the management of pests throughout the world. In many ways we constitute a huge fraternity, working well together, exchanging information and tips in the best spirit of professional cooperation.

On that day and over much of the next twelve months, at least once a month and sometimes more often, the nationwide pest management service visited David and Adette’s house and used its accumulated expertise to apply the most advanced pesticidal formulations on the market. Their highly trained technicians diligently and professionally applied those pesticides around the home’s exterior, inside the home, and inside the home’s spacious attic.

The result? Multitudes of live scorpions were killed outright. The attic floor of David and Adette’s house was literally covered with their carcasses. Yet — as long as pesticides remained the primary approach to controlling them — the onslaught of new, fully grown, and medium sized scorpions continued, practically unabated.

Except during the winter months.

During the cold wintertime the number of scorpions found inside David and Adette’s home quickly diminished to zero. That condition, of zero scorpion incursions, lasted as long as the cold weather continued, which for the relatively cold winter of 2009-2010 spanned four months. Later, when temperatures climbed again, the scorpions returned with a vengeance.

This reveals a crucial fact and unmasks a common fallacy: the scorpions were not being warehoused in the skin or attic of this home, as David and Adette had been led to believe. Their pest control technician had told them that this kind of warehousing was taking place, probably because the company training program said so. The technician’s strategy, based on that presumption, was to strike the scorpion infestation “at its source,” that is, inside the home itself, and in the yard immediately around the home, expecting to eliminate the scorpion infestation entirely via that means alone. And, had the underlying presumption been correct, that strategy would probably have been successful.

What the technician didn’t realize was that the source of the scorpions was not the house, but the forest environment around the home and its yard. The scorpions lived in the wood piles, brush, and leaf litter, as well as in the thick woods nearby. These animals only came to the home and its yard because they could track and capture abundant prey there, on the outside, in the trees, and in the landscaping. Once the prey was gone (i.e., when wintertime arrived, and normal yard insects died out) the scorpions migrated back to the thick woods, where prey still could be found in the thick, protective, vegetative litter of the forest floor.

Striped bark scorpions live, on average, from 2-5 years (Beccaloni, 2009, p. 269), and are rather good at adapting to changing weather conditions. They are quite able to go without food for up to a year without starving, and cold weather is not lethal unless temperatures drop significantly below freezing and remain there for extended periods. In fact, the striped bark scorpion is known to recover, even after being frozen stiff, due to certain unusual physiological properties (Whitmore et al., 1985).

Had these scorpions insisted on living in the skin and attic of David and Adette’s home throughout the year, most would likely have survived the cold winter months. However, during those months they would have continued to forage for food nocturnally, as in the warmer months, leading to encounters with David and Adette from time to time. Yet, during the winter, such encounters never took place.

This suggests that, instead of inhabiting David and Adette’s home, they simply exploited it as a source of food (and a temporary place of refuge after falling out of the trees, while traveling from the roof back to the yard) as long as the food they preferred — mostly insects — could be found there. Once the insects disappeared, the scorpions migrated to the surrounding forest, where insect life could still be found in the thick leaf litter of the forest floor.

A study of the microhabitat preferences for Centruroides vittatus (McReynolds, 2008) indicates that this scorpion’s choice of habitat is highly influenced by prey availability, though foraging potential (another measure of prey availability) and refuge from predators figured into the picture as well. This is important. The moment striped bark scorpions cease being able to track and capture prey in a given area, they abandon that area and return to the deep leaf litter and thick underbrush of the deep woods, where terrestrial insects can survive and thrive throughout the year.

The mix of these land-based insects in the deep, wintertime forest is nowhere near as attractive as those found during the spring, summer and fall around a residential dwelling whose lights attract juicy, delicious flying bugs all night long. But it still beats going hungry. And during the wintertime there are no flying bugs around, anywhere, period.

Striped Bark Scorpion (Centruroides vittatus), dorsofacial; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), dorsofacial; Cedar Creek, Texas–06.18.10

David and Adette’s home, compared with the surrounding forest, provides a set of special conditions that set in motion a predictable sequence of events.

Here we have a large residential dwelling in the midst of a thick woodland. In the spring, summer and fall the lighting in and around this home serves as a luminous oasis in what is otherwise a sea of darkness. As such, it attracts huge numbers of flying insects that provide an unlimited food supply for scorpions throughout the night, when scorpions are most active.

The lights, whether outside direct lighting, or interior indirect lighting that shines through the home’s windows, only have to be on for a short time after dark to attract huge numbers of flying insects, out of the surrounding woods, to the trees, shrubs, and grasses nearby.

The insects mate, lay eggs, and feed here in greater abundance, not only because of the lighting, but also because places of human habitation provide other food sources not available in the woods. The combination of lighting and food sets up a cycle of life that becomes more pronounced as spring proceeds into summer, and summer leads into fall. Even a tiny population of scorpions from the surrounding woods would grow, under such conditions, into a much greater number after a few years.

This would not happen quickly, however. The striped bark scorpion female has an average gestation period of eight months, between fertilization by a male and emergence of young. A steady increase in scorpions would occur because of the dynamics of prey availability right here, near the dwelling, but not elsewhere in the surrounding forest. Each succeeding year, when winter comes, the steadily increasing population of scorpions is forced to retreat, back to the woods. There it quickly decimates the insects endemic to such places. That does not reduce the scorpion population, since scorpions are able to survive for months without food if need be, but it wipes out the insect food in the forest and — as a result — produces a huge, voracious, but latent population of scorpions that is poised, as on a springboard, to hurl itself en masse toward any source of live insects that later becomes available.

After spring arrives,the moment it becomes clear to the scorpions that fresh supplies of flying insects are waiting to be eaten in David and Adette’s yard, wave after wave of hungry scorpions leave the impoverished forest to feed on them there once more.

Under these conditions, an almost unlimited number of scorpions is found vying, each spring, for the chance to take part in the feeding frenzy. Treating the home and yard with pesticides will have little to no effect on these hungry arachnids. You can kill thousands of them, and thousands more will take their place, for as long as they find insects to eat.

What is needed is to reduce the number of flying insects, and simultaneously make it difficult for scorpions to recognize their presence. PestAvoidance, through habitat modification, does both. Pesticide applications, however, do neither.

So, a full year passed…

When it became obvious that pesticides were not getting the job done, David and Adette consulted me once more, in desperation, regarding their options. They’d canceled the pest management contract with the nationwide company because they’d failed to bring the scorpions under control. Under the circumstances, they were giving serious thought to the prospect of selling the ranch and moving away. This was a painful idea, because — except for the scorpions — they loved that ranch and the prospects it held for the extensive set of kennels of their dreams. Now at their wit’s end, moving was preferable to subjecting themselves to the constant threat of being stung. Though they’d not experienced many stings, the risk was always present, and each stinging event increased the possibility they would acquire a dangerous sensitivity to the scorpion’s venom.

I asked David and Adette if they were finally ready to consider some of the ideas that we’d discussed a year earlier. Back then, those ideas didn’t make a lot of sense. Now, with the option of using traditional pesticides off the table, they were ready to explore those other solutions with open minds.

It made sense to drive out to their ranch, after dark, to survey the yard and home with an ultraviolet flashlight. Scorpions fluoresce a bright lime-green under UV illumination, making them easy to spot. My kit contains several extra safety glasses with UV filters, so all three of us could conduct the survey together. That night, we found over 50 scorpions on the exterior of the home, in the trees, and in the grass. Inside the home we found a scorpion on the floor of the darkened kitchen pantry, and several more inside their floored attic, concentrated around a laminated wooden beam where it appeared that scorpions that had fallen onto the roof were taking temporary refuge. They told me that most of the scorpions they’d been finding inside the home were focused in the living room, on or near the wall where the laminated beam connected to the foundation at ground level.

After the survey was complete, we sat down in their spacious dining room and discussed what we’d seen. The scorpions inside the house were not as numerous as those outside. Obviously, the scorpions preferred the outdoors. It would not take much to make the indoors even less attractive. Concentrating on the habitat modifications we’d discussed early on, and using liquid and granulated habitat modification sprays and mulch should produce positive results immediately.

OK, so now what, Jerry?” Adette asked.Seeing all those scorpions outside had shaken her up a bit, and it showed in her voice.

“Did you notice how many scorpions we found outside, and how few we found in your home?” They nodded. “It’s obvious they don’t really want to get inside, and once they get in, all they want to do is leave. If you apply the herbal spray aggressively inside, especially in the places where you’ve been seeing the scorpions, and do the same thing around that laminated beam in the attic, you will probably stop seeing so many inside. But you have to be aggressive with the spray. A half-hearted effort worn’t work. Plus, you need to do the same thing around the exterior walls of your home where we saw the scorpions tonight, and you need to apply lots of the herbal granules in the yard, particularly around the perimeter of the home, the perimeters of the trees where the scorpions have to travel to get to the tree trunks. All that, combined with getting all the litter, woodpiles, brushpiles, and similar materials that scorpions can hide in, out of the yard, and voila! your worst experiences with scorpions should be behind you.”

“Really?” Adette murmured. “That’s all we have to do?”

Yes, I told her. That’s all she and David had to do.

Immediately, they redoubled their mechanical habitat modification work on the yard and trees, and began applying the liquid and granular habitat modifiers I provided, in concentrated amounts, both in the attic and around the perimeter of the home. And they did this all by themselves. That is — to my way of thinking — the best approach of all because they are there all the time and nobody knows their yard and home as well as they do.

As expected, the number of scorpions decreased dramatically. Within weeks, they were reduced to the point that they are, today, only rarely encountered inside their home or even in the yard. David and Adette no longer think about moving out. Today their home is — well — the Home Sweet Home it was always supposed to be.

But the scorpions did not disappear entirely. The conditions that raised them up to such high levels in the first place are not quite gone yet. Much work still needs to be done to reduce and eliminate harborage in the immediate perimeter of this home, and in the outbuildings into which David is expanding his kennels and corrals. Furthermore, our research at other sites plagued with scorpions is pointing to additional habitat modification methods that should synergize with those mentioned above. One of the most promising of these involves management of exterior lighting.

In any case, the scorpion situation at David and Adette’s home continues to improve. Months, even years, will probably go by before all the necessary mechanical habitat modifications are completed, but David and Adette are moving things in the right direction. And they are doing it safely, without pesticides.

As initially explained to them, PestAvoidance is not an event; it’s a process.

This post documents the work being done at this ranch residence. The object is to help David and Adette maintain the peace and tranquility that came once the nightly onslaught of these pests ceased.

In the process it has been possible to shed some light on the biology of the striped-bark scorpions. We’ve analyzed, at their ranch, the effectiveness of various PestAvoidance strategies that we’ve used, and proven that method’s effectiveness, not only in the long run, but also right away.

Biology of the striped bark scorpion (Centruroides vittatus)

This is only one of ninety species of scorpions found in the United States. Eighteen different species are found in Texas. Among these, the striped bark scorpion is unique in being found throughout the state.

It is also unique in its propensity for climbing tall trees and the walls of structures. Most other scorpion species are primarily ground dwellers, but not this one; you are, in fact, more likely to find these up a tree or on the undersides of eaves than crawling on the ground.

It is crucial, in order to understand how to deal with these organisms, to have more than a rudimentary understanding of their anatomy and biology. To that end, the following notes are provided:

The scorpion is comprised of a long, five-segmented posterior body portion often called a tail (a misnomer, as the scorpion “tail” is actually a complex extension of the body’s digestive system, the metasoma, that contains the proctodeum, or hindgut and anus, the latter opening near the telson, at the distal end of the metasoma), that is attached to an elliptical body.

At the tip of the metasoma, attached to the fifth metasomal segment, is an enlarged, bulbous structure known as the telson.

Striped Bark Scorpion (Centruroides vittatus), lateral telson; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), lateral telson; Cedar Creek, Texas–06.18.10

The telson, which contains a venom sac (lumen) and the musculature needed to forcefully eject the venom, is clad in a hard chitinous covering that terminates in a long, slender, sharply-pointed stinger (see the photo below).

As with all arachnids, the body is equipped with eight legs.

Projecting outward from the face is a pair of strong pedipalps fitted distally with  enlarged  pincers.

Scorpions are ancient organisms. Fossil evidence, dating from as far back as 350-400 million years ago, indicates that few changes have occurred to their basic anatomical structure in the interim.

That they have not changed much over all those years, yet have not only survived but thrived, tells us something very important. Their ancient anatomical structure has served them well, without the need of serious modifications.

It allowed them then, and still allows them today, to secure their food in sufficient quantity to establish a healthy presence in a variety of locales.

It also enabled them to reproduce and successfully compete with all the other organisms that — then and now — occupy the various locales where they are found.

That’s saying something.

Striped Bark Scorpion (Centruroides vittatus), vemtrum; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), vemtrum; Cedar Creek, Texas–06.18.10

Few organisms can claim a similar legacy.

The Red Queen Principle of Selective Adaptation has not, from all outward appearances, figured nearly as prominently in the evolutionary biology of this animal as it has with most other organisms.

By way of example, the European honey bee (Apis mellifera) that pollinates crops all over America today, is quite unlike the primitive wasp that preceded it, only 100 million years ago.

Ancient nectar feeders and pollinators, like that primitive wasp, had to adapt in dramatic ways, and do it in relatively short time frames, just to keep up with the rapidly developing botanicals they gathered nectar and pollen from.

When such organisms failed to adapt, they failed to survive, and the evidence of that lies in the easily observable fact that those primitive wasps are not flying around today.

Not the scorpion. Today’s scorpion looks almost exactly like its ancestors did, hundreds of millions of years ago.


The answer to that question cannot be provided in a simplistic way. However, we can point to a couple of simple facts that hint to that deeper answer.

Striped Bark Scorpion (Centruroides vittatus), pectines; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), pectines; Cedar Creek, Texas–06.18.10

Scorpions are nocturnally-active, non-selective insectivores that use simple, but effective techniques to find, secure, subdue, and consume their prey.

They use seemingly primitive, but consummately effective, structures and methods to find mates, transfer sperm, fertilize eggs, and produce prodigious numbers of young.

They have two primary eyes on the top of their heads, and clusters of simple eyes that line the forward edge of the face; these eyes are weak, and are not used to locate prey or mates.

Other anatomical structures are used for that purpose.

One of the more interesting of the latter anatomical structures, essentially unique to scorpions (though structurally–but apparently not functionally–analogous structures are described on the bills of ducks, and interior to the avian eye), are the scorpion’s pectines.

The pectines are comb-like (or, like me, you may see them more as brush-like) appendages projecting down from the underside of the body.

The pectines sweep the ground as the scorpion moves about. These are specialized sensory structures that enable the scorpion to detect, and follow, minute traces of pheromones in the environment, and much of the scorpion’s brain tissue is devoted to interpreting signals from the nerve endings in the pectine extremities. Because of the importance of this structure, anything that interferes with its functioning creates serious difficulties for the scorpion. Habitat modifier sprays and mulches are believed to produce serious interference to the point that the scorpion cannot tell very much about its environment while in the presence of such modifiers. It isn’t long, under such circumstances, before the scorpion leaves the area for more “telling” locales, not because it has encountered a repellant, but simply because its detection and analysis equipment works better elsewhere.

Striped Bark Scorpion (Centruroides vittatus), frontofacial; Cedar Creek, Texas--06.18.10

Striped Bark Scorpion (Centruroides vittatus), frontofacial; Cedar Creek, Texas–06.18.10

The pectines may also help the male determine where to deposit the spermatophore during mating.

A scorpion that is unable to use its pectines for locating food or mates is essentially blind, because although the eyes are still functional, they are not used for those purposes by this animal.

Thus, an environment that produces confusing and overpowering stimulation of the scorpion’s pectines neither attracts or nurtures that organism.

In such an environment, the scorpion is unable to function normally, and as a result, over time, such environments would be expected to contain few or no scorpions at all, not because those areas are repugnant to them, but because they have nothing to attract them there. That’s why non-toxic habitat modifiers work so well in PestAvoidance projects.

As generalist predators, scorpions can survive regardless of the mix of insects and spiders that they encounter.

And though those insects and spiders have changed a lot over the millennia, for the most part they’ve never managed to develop effective strategies or defensive structures that prevent scorpions from making a meal of them when the two meet face to face.

As you can see, scorpions in general, and striped bark scorpions in particular, are not ordinary creatures.

We would be wise to recognize that they cannot be dealt with using ordinary methodologies.



— Questions? Corrections? Comments? Feel free to e-mail You may also leave a comment in the space provided below.

4 thoughts on “An Invasion of Striped Bark Scorpions at a Residence in Cedar Creek, Texas

  1. davidsoliz Jul 12,2010 10:44 pm

    …thanks for all your work mr. cates. we appreciate what you do! semper fi.

  2. Paula T Jul 31,2010 10:44 pm

    We also live in Cedar Creek and have a problem with the scorpions being inside the house. We have gone so far as to make certain that all the drains are plugged at night before we go to bed. We have found them in the tubs, sinks and toilets. Very nasty little buggers and have not found anything that mentions eradicating them. I threw a live one in the toilet thinking it would drown but it only crawled around under water for the longest time. Do they live in the septic systems?


    Editor’s Note: All scorpions love wet locales and congregate around water sources in the midst of otherwise dry environments. However, although striped bark scorpions can survive underwater for long periods of time they do not usually swim or bathe in water the way many snakes do.

    In our laboratory, we keep several dozen striped bark scorpions, for study, in vivariums containing litter, blocks of wood and small rocks to hide under. We also include small bowls of water for drinking purposes. They drink the water, but they don’t bathe in it. Consequently, it seems doubtful that they live in sewers or in septic tanks in large numbers under ordinary conditions. You are finding them in bathtubs and sinks because they fall into those structures while foraging in your home, and then cannot climb up the smooth vertical surfaces to get out.

    Our studies at the site discussed here, in Cedar Creek, suggest strongly that the striped bark scorpion prefers dark, damp places during the day, and forages within a somewhat limited habitat during the nighttime hours. Most species of scorpions are poor climbers, and do not generally climb trees. However, the striped bark scorpion is an exception, being an excellent climber on textured or rough surfaces (though they are unable to climb vertical glass or plastic surfaces). As a result, the trees in its midst are as much a part of its natural habitat as anything else. In fact, it tends to spend more time foraging in the trees than on the ground, probably because it finds abundant prey on tree limbs and in leafy bowers. Yet, during prey capture and immobilization, and even while ambulating through its aerial habitat, it is not unusual for these arachnids to lose their footing and fall. This is not a problem for the scorpion, as its body is light enough that even a long fall to the ground will not produce injuries, but it explains how they end up in attics and homes so often in some places.

    Its love of trees means that, if any tree limbs extend over the roof of a home, the striped bark scorpions on those limbs will fall, with regularity, on that roof. When this happens, some will enter the attic and eventually emerge in the living space of the residence below. Therefore, trimming the limbs of nearby trees so they do not overhang the roof is an essential habitat modification that must be carried out to control striped bark scorpions where they are noticed.

    Trimming trees back from homes so they do not overhang the roof probably eliminates as much as 85-90% of the scorpions that are are infesting a home. However, in some homes, due to the huge trees nearby, and for other reasons, it is impractical or impossible to trim the overhanging limbs completely or at all. Furthermore, even with homes whose habitats can be modified in this manner, as long as a large number of scorpions (of whatever species, including those that do not forage in trees) forage in the yard all night long, the risk that some will enter the home via a variety of routes is very great. Because of this fact, additional habitat modifications are in order beyond trimming the tree limbs.


  3. atxgo Oct 21,2010 10:49 pm

    Great article. I recently purchased a home in Dripping Springs, and have a bad scorpion infestation. I have been told by multiple people that bark scorpions love to nest in cedar trees. My property is covered in cedars, many within a few feet of the house, although not overhanging the roof. In your opinion, is the claim that cedars are a breeding ground for scorpions a myth or is there some legitimacy to the claim? Also, I plan to clear the cedars anyway this winter. Should I subsequently expect the scorpions to invade my house in retaliation?


    Editor’s Note: In the Cedar Creek home described here, the scorpions were infesting oak trees, and they were found in those oak trees in large numbers. My presumption has been that they were there only because they found considerable prey in the oaks.

    My recollection is that we never found any in the cedars nearby, though we did look for them using UV lighting in those cedars after dark.

    As I continue to study and test the PestAvoidance™ concept, I’ve noticed that the combination of predator/prey relationships, and habitat selection pressures, seem to be particularly significant determinants bearing on where predators forage and nest.

    With respect to predator/prey relationships, scorpions are consummate nocturnal predators that generally forage at night, and only where they find abundant prey. They avoid foraging in the daylight, and they avoid areas where prey is non-existent or in short supply. During each nocturnal foraging exercise, they use pheromones, auditory stimuli, and similar evidence that can be sampled remotely. to home in on fruitful predation sites. If it happens that cedar trees provide lucrative hunting-grounds for scorpions, I would expect them to be present in appropriate numbers. If not, they will eschew the cedar trees, at least for purposes of predation.

    On the other hand, the need for secure habitat could dictate that the cedar trees be exploited during the daylight hours, especially if they happen to provide superior protection from organisms that might prey on scorpions while they are nesting and breeding in their diurnal habitats. The need for such habitat would seem to be great, but only if it is available within a reasonable distance from locales containing abundant prey.

    The striped bark scorpion is an extremely sociable creature that congregates during the day in relatively large groups of its own kind. Cannibalism–which is common among certain other scorpion species–is rare to non-existent in groups of nesting striped bark scorpions, even during periods of extreme food scarcity. One collection of this species of scorpions that I’m studying in the lab is only fed once a month, and during the intervening period they aggregate in tight clusters of 10-20 individuals that form layers up to three individuals deep, seemingly with little or no strife. When I count the individuals in the container each month, the number of adults remains the same. Obviously, inasmuch as the collection has not added to its numbers, the adults are likely consuming each new brood that emerges, but that’s another story.

    As for your question about whether the scorpions might attack the house to retaliate against you for felling the cedars, that seems unlikely. Again, the scorpions go where hunting is good, and they stay away from locales where they go hungry. An exception to that rule occurs, as demonstrated at the site in Cedar Creek, when tree limbs containing abundant prey stretch out over a structure. It is not unusual for the scorpion and its prey to fall out of the tree during the predatory attack and ensuing struggle, and if such a scorpion lands on a roof it will eventually enter the structure to find its way back to the ground. When I find large numbers of scorpions inside a home, I usually find a few tree limbs stretched out over the roof of that home.

    My point is that if you have no limbs over your roof, you should not expect to see lots of scorpions inside your home unless–for some reason–they have reason to view your home as either (1) a source of prey or (2) a good place to nest during the day.

    Maybe we should do a survey at your property, after dark with a UV light, to see where the scorpions are concentrated. If they are in the cedar trees, we’ll find them there, but if not we’ll find out precisely where they are. Let’s schedule this one day soon and see what we find out.


  4. Mike Jul 23,2014 9:42 pm

    Maybe I missed it… What did you use as a non-toxic habitat modifier? I’m in Las Vegas and we’re experiencing a huge problem throughout the valley with Arizona Bark Scorpions. Any help or advice you can offer would be awesome!


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