What Can Brown Do for You?

A step-by-step plan of one company's residential brown recluse spider program.

April 25, 2007

When you say “brown recluse spider” it causes many different types of reactions. These spiders certainly elicit fear, thoughts of pain and the need for self-preservation. Many have seen pictures of bites or have known someone who has been bitten, but many such bites are not brown recluse bites at all. A common first conclusion is to attribute every serious bite to the brown recluse, but it is difficult to determine immediately which pest did the biting. If you have a brown recluse bite, it does not swell up; it goes deep into the skin. This type of severe reaction does not happen to many people, but it does happen occasionally.

Our company, Holper Pest & Animal Solutions, treats a lot of homes with brown recluse spider infestations and few customers have even been bitten. Of the few that have, some have been hospitalized and some have not required hospitalization. I once went to a home and the homeowner told me that if I didn’t fix her problem, she was going to sell her house. She had become so frightened that she was terrified when she saw any spider. Even though the risk may not be that great, if you have brown recluse spiders, you have a risk of being bitten, and it’s important to control the population. Brown recluses eat many other insects, but their risks outweigh their benefits.

So what type of house could have a brown recluse spider problem? Many types of houses provide the right environment for brown recluse spiders. Examples include a one-story shingled roof with little vegetation close to the house, but with 8 feet of ivy around the perimeter and a shake-shingled roof.

The worst houses in my area of the country (St. Louis, Mo.) seem to be the older brick homes with thicker vegetation. They may be between 60 and 100 years old, providing many harborages for this secretive species of spider.

THE FIRST STEP. Every effective treatment begins with a thorough inspection. Searching the house you will find either spiders or webs. In the basement and attic you easily may find webs in the corners or the rafters. A brown recluse web is abstract without much form to it. It could be mistaken for lint or dust. Very often you will find shed skins. As a recluse grows, it lies on its back and sheds its skin to grow to the next size. If you don’t find anything in the initial inspection, then the best option may be to place insect monitors to evaluate if you have any spiders around. At my company, when we put out monitors, we put out a lot of them. We may put out four or five to a room, depending on its size. I want monitors on each side of each door of the house; under every bed, sink, and toilet; under dressers; in the basement (throughout); and in the garage. Up in the attic is a great place, too. When placing monitors you want to put them right next to the wall. Brown recluses like to travel along walls. When I catch a spider, I write on the monitor how many brown recluses I caught and the date. We then will look at the monitors on the follow-up visits to determine the intensity of the problem. I prefer to leave monitors in place that have caught spiders; they act as bait for the next spider. I may leave monitors in place for a long time but if they get dusty then I replace them. The monitors tell the story of how and where the problem is or if there is one at all. When we achieve thorough control in a house we will then keep monitors only in key places.

Our company’s policy is that we inspect and then treat accordingly. Our follow-up visit usually will occur within a month of the initial service or inspection. We normally will service a home that has a problem three months in a row, then quarterly after that.

Our threshold is six brown recluse spiders. If we find more than six spiders we will implement our “Brown Recluse Program” (which I have been describing). If we find fewer than six spiders, a general spray should be sufficient. We also look at the rooms with spiders and see if there are any factors that are leading to the problem. Some rooms may have no activity at all, while others may be overrun.

In one of our worst cases, we caught more than 700 brown recluses on monitors in a six-month period, but after treatment, it is rare to catch even one on a monitor. I also find that if the outside conditions are conducive to brown recluses (close vegetation, old tuck pointing, etc.) reintroduction to the structure is almost inevitable. Power sprays on the outside can help keep the population to a minimum but there still could be a yearly problem. In these cases, we perform a May, June and July spray service every year, then quarterly. This will protect the house in a way that will keep it pest free. In older homes, sealing and caulking may be an option, but sometimes you have the house that you can’t seal. Old tile roofs and bad fascia boards provide opportunities for pests to enter.

THE PLAN OF ATTACK. We find a lot of homes where, on the initial inspection, brown recluse spiders have overrun the house. There is no question if they have a problem it is how bad is the problem? The initial service entails treating the baseboard area of the house in the known problem areas. Then in those areas use an Actisol machine or a Micro-Injector to treat the voids. Dusting into the voids can be effective. If the spiders are active they may run into the treated area or into a monitor.

If you perform a treatment at this level you can do the follow up faster. On this subject, there are a lot of opinions saying that spraying does not control spider populations. Experience is the best judge, and from my experience, it is effective. A microencapsulated product is appropriate for this type of treatment. We often find a lot of dead spiders along the walls.

To those customers that have a lot of dust or old webbing with the shed skins, we offer to vacuum the rafters and corners where needed. This aids in the reinspection as we are able to see if any new webs have formed.

Generally we schedule our follow-up appointments for 30 days. When you come back, look at every monitor you previously set. What is on the monitors determines the next step. If you have a significant increase on the monitors, then you determine where the increase is and treat it accordingly. If there is no increase, set up the next time you want to service. Then start over again, inspect the monitors and go from there.

We find that homes on regular quarterly service seldom develop any major pest problems. That’s because it is much easier to prevent insect infestations than to solve them once they are established. Therefore, when in doubt, take a proactive approach to the business.

Treating a home for brown recluse spiders can be challenging and rewarding. Where there once was fear, you “give them their house back.” Security in their own homes is the best thing we can provide our customers.

The author is president of Holper Pest & Animal Solutions, St. Louis, Mo. He can be reached at jholper@giemedia.com.



Some 54 species of Loxosceles are known to occur in North America, Central America and the West Indies. The brown recluse spider, Loxosceles reclusa, is one of 13 Loxosceles species now known to occur in the United States. At the beginning of the 20th century, only two species were recognized — L. rufescens and L. unicolor. Brown spiders of the genus Loxosceles (also known as violin or fiddle-back spiders because of the violin-shaped marking on the carapace of some species) are known from two principal world areas: temperate South Africa northward through the tropics into the Mediterranean region and southern Europe; and temperate and tropical zones of North and South America.

In the United States, the brown recluse spider, L. reclusa Gertsch and Mulaik, is considered to be the most widespread and most important species of this group. Of lesser importance are the Arizona recluse, L. arizonica Gertsch & Mulaik; the Texas recluse, L. devia Gertsch & Mulaik; and the desert recluse, L. deserta Gertsch, native to the Southwest.

The Chilean brown spider, L. laeta, has a particularly serious bite but is only established in small parts of Southern California. Another imported species, the Mediterranean recluse, L. rufescens, occurs in southeastern states along the coast. This spider’s propensity for inhabiting household goods, furnishings, etc., enabled it to be imported in overseas shipments.

Distribution. The natural range of the brown recluse spider, L. reclusa, is from southern Texas north to Nebraska, and east to eastern Tennessee and Alabama. It appears to be most highly concentrated in the south-central portion of the Midwest. Although reports of brown recluse spiders outside its natural range from Maine to California have occurred, these are more likely due to transport of commerce or domestic household goods. In California, fewer than 10 cases of L. reclusa have been confirmed. Specimens collected in California are usually the desert recluse, L. deserta, whose presence inside buildings is less common and whose bite is less toxic.

The Chilean brown spider, L. laeta, occurs in Los Angeles but is usually found in dark basements of commercial and public buildings. This species was also found in a residence in Winter Haven, Fla., in 2002.

In addition, many misidentifications occur from similarly colored spiders. Numerous identifications of brown recluse spiders occur in the absence of a specimen simply based upon examination of wounds in skin. Physicians may be too quick to decide that an open ulcerous wound is the result of a brown recluse spider bite, even in those areas where this species is not known to occur. Such misidentifications can lead to delays in appropriate care if specific treatments are available for the actual cause of the wound.

Within its range, the brown recluse naturally occurs in outdoor situations, living in piles of debris, utility boxes, wood piles and vehicles, as well as under bark, logs and stones. It has adapted quite well to indoor habitats where it is commonly found harboring in storage areas, such as closets, attics, crawlspaces, cellars, and other dark recesses. They frequently inhabit clothing, boxes, toys, papers, furniture and other household items and seem to prefer “layered” situations, such as stacks of items or clutter.

Preying Habits. The brown spiders are nocturnal and search for food such as silverfish, cockroaches, crickets or other soft-bodied species. At first light, wandering spiders will normally return to their retreat of an irregularly spun, off-white web with their prey. Males wander farther than females and are the sex that most commonly crawls into shoes, trousers or other clothing; or under sheets and covers on beds. Bites occur when a spider hiding in clothing or bedding is accidentally trapped against the skin. The thin, wispy webs of the brown recluse may be seen in drawers, boxes, shelf, corners, under furniture or other undisturbed areas.

Life History. After mating, which may occur from February to October within its natural range, 40 to 50 eggs are deposited in off-white, round, 1/4-inch (6 mm) diameter silken cases. The summer months of May through August are optimal times for egg production. From one to five egg sacs will be produced during the female’s lifetime, which normally averages one to two years; however, four to five years is not uncommon. The presence of shed skins (exuviae) and subsequent attachment in and around residences may be indicative of infestations and enable accurate identification. They are relatively long-lived, averaging a two- to four-year life span. Additionally, the brown recluse is “synanthropic” which means its numbers increase when living within human dwellings. When one brown recluse is found, numerous spiders usually can be located by visual inspection or the use of monitoring traps.

Recognition of Brown Recluse Spiders. Most Loxosceles possess the characteristic dark brown violin marking on the dorsal carapace, but in some species or individual specimens this marking may be faded or absent. Six eyes are situated in three pairs arranged in a semicircle pattern. The body coloration of the brown recluse spider varies from yellowish to light tan to dark brown and is covered with a fine pubescence. The spiderlings resemble adults in structure but have somewhat lighter coloration and may lack the violin-shaped marking on the carapace.

The preceding information was excerpted from the Mallis Handbook of Pest Control. This chapter was revised by Stoy A. Hedges, who also served as editorial director of the ninth edition of Mallis. To order, call 800/456-0707 or visit www.pctonline.com/store.