We can all sleep, literally and figuratively, a little better since outhouses have mostly disappeared in the United States. Aside from the inconvenience and disruption to sleep by wandering outside at midnight, the advent of indoor toilets greatly reduced bites from black widow spiders. The midnight venture to unsound structures, with many gaps and holes, invited spider mischief before housing regulations were enforced and exclusion practices became pest control common knowledge. Thankfully, today’s building codes and sealed structures means that spider bites are a rare occurrence, especially from a venomous spider species. However, as a pest control operator, you may not think spider bites are rare by the quantity of spider questions from clients and the number of people who swear they have been bitten by a spider.
There are only a handful of spiders that are venomous in the United States. Thus, learning to identify the medically relevant species can help you easily put your customers’ minds at ease. Aside from the venomous spiders, there are several tricks you can use to help control unsightly webs around homes and manage other common house spiders as well.
GENERAL SPIDER BIOLOGY
Spiders are not insects and are grouped into the class Arachnida. Spiders have two body regions, the cephalothorax, which contains the head and legs, plus an abdomen. Instead of separate head and thorax regions like insects, spiders have a fused head and thorax region, hence the name cephalothorax. Typically, spiders have 6-8 eyes that are arranged in rows and the patterning of spider eyes is a key characteristic used for spider identification.
Many spiders will lay egg sacs in and around the web but there are some species of spiders that carry their egg sac until hatching. After hatching, the spiderlings will often climb up a vertical surface, produce a long twine of silk and hang on while the wind carries them off. This is one way that young spiders disperse to new areas, called ballooning. The average lifespan of most spiders is one year but it is species-dependent, with some wolf and larger spiders living several years.
Spiders can be extremely beneficial since they are predators and feed on many insect pests. Thus, spiders can act as a form of biological control around homes and gardens. Spiders often wander indoors in fall when temperatures cool down and in the spring as temperatures increase. These two times of year often cause an increase in customer calls for spiders.
COMMON SPIDER GROUPS FOUND AROUND THE HOUSE
Orb weavers—family Araneidae: Orb weavers spin flat, circular webs that are typical of what most people think of when it comes to spider webs. These spiders have large, round abdomens and are slow moving spiders that wait for their prey to be captured in their webs. Webs are often found along corners and other areas around buildings as well as in vegetation, and can often be found around landscaping of homes. These spiders rely on the vibrations in their webs, not their eyesight, to find and capture prey.
Funnel weaver spiders—family Agelenidae: Funnel weaver spiders produce dense silk webs in shrubs and grass and around bushes. The spiders sit and wait down in the hole of the funnel for prey and will quickly emerge to capture prey that is stuck on their webbing. These spiders typically have longitudinal stripes along their cephalothorax and long spinnerets used for spinning their funnel webs.
Jumping spiders—family Salticidae: These spiders do not create webs but are active hunters that will pursue their prey, and can easily be distinguished by their ability to jump great distances compared to their body length. They are usually less alarming to homeowners since they do not create webs and are typically smaller in size and less frightening in appearance. Many jumping spiders are metallic in color.
Cellar spiders—family Pholcidae: Cellar spiders are found in dark corners in garages, cellars, basements and crawl spaces that are dark and well protected. These spiders have long legs with untidy webs that can be large. When disturbed, they will vibrate or bounce in their webs.
MEDICALLY IMPORTANT U.S. SPIDERS
Widow spiders (Lactrodectus species): Widow spiders can be found in every state throughout the United States. They prefer protected areas and are often found in dark corners of basements, garages, cellars and crawl spaces but also outdoors around fire piles, shrubbery and other structures that offer protection. One of the most common widow spiders, the black widow, is shiny black in color with a characteristic red hourglass shape on the bottom of the abdomen. Widow venom contains a neurotoxin that can result in intense pain at the bite site and in extreme cases cause nausea, chills, fever and labored breathing.
Recluse spiders (Loxosceles species): There are 13 species of recluse spiders in the United States. Most species have a characteristic brown violin shape on the back of their cephalothorax. Recluse spiders can be found in a variety of places around the home but are always in dark, undisturbed areas. Their bites contain a potent cytotoxin that breaks down the cells of tissues, causing swelling and intense pain at the bite site and in severe cases can result in larger, open lesions.
Completely eliminating spiders and their webs around homes is next to impossible and requires managing expectations and customer communication. Spiders will quickly recolonize an area and rebuild their webs. When dewebbing, you want to dust first and try to contact the spider prior to dewebbing so that the spider does not survive and recreate the web. Sticky traps should be used for monitoring for spiders in areas where they frequent as well as behind furniture and other dry, dark areas. When treating, focus attention to wall voids, behind baseboards, door and window trims, under bathtubs, cabinets and other cracks and crevices around garages, attics and basements. Spot treatment of corners and soffits and keeping lights off to decrease attraction of prey for spiders around the exterior may also be helpful for spider control. Indoors, vacuums can be used to suck up and then discard the webs, spiders and egg sacs.