Spiders are found on every continent, except Antarctica, and can live in almost any habitat. As of 2015, there are 45,700 known species of spiders.1 If you have arachnophobia, a fear of spiders, these stats might make you shudder, but spiders are actually misunderstood in many ways. You still don’t want them in your home, but spiders in your garden can do a world of good. This Ultimate Guide to spiders will walk you through the benefits and dangers of spiders and teach you how to prevent and control them using effective products.
Spiders are arachnids and are closely related to scorpions, mites, and ticks. They have eight legs, 2 body segments with jointed limbs, and most have four pairs of eyes. Spiders came on the scene 300 million years ago and still flourish today because of their many adaptations. Spiders developed spinnerets that release silk to make webs. Most species of spiders capture their prey by using these sticky webs, but others are active hunters and chase down their prey. Spiders eat mostly insects, but some very large species may also eat birds or lizards.
The Benefits of Spiders
Many people fear spiders because of their venomous bite, but spiders can actually be beneficial in many ways. A study in “The Science of Nature” estimates that the 25 million tons of spiders on earth kill 400-500 million tons of prey each year, mostly insects. Spiders are insect-eating machines and can keep them at bay in your garden and around your home. They help control flies, mosquitoes, beetles, moths, wasps, and many more.
There is also some hope that spider venom can be used as the next great pesticide because it is toxic to nuisance insects, but harmless to bees. Scientists are specifically looking at the Australian funnel web spiders because they thrive in captivity and are easy to milk.2 Scientists are also studying spider venom for medical uses like cardiac arrhythmia, alzheimer’s, and strokes. It may turn out that spiders are more valuable than any of us realize.
Dangerous Spiders in the U.S.
Although there are many reasons that spiders are beneficial, they do occasionally bite humans, and some bites can be painful and even life threatening. Spiders use venom to capture and kill their prey. Luckily, most spider venom is harmless to humans, and spiders usually only bite if disturbed or frightened. Some spiders’ venom can cause moderate pain, but is unlikely to be a major health concern. These types include: orb weavers, tarantulas, wolf spiders, and jumping spiders. In the United States, there are really only two types of spiders that pose a health risk for humans: black widows and brown recluses. While bites from these two types of spiders do pose potentially serious concerns, they are still very unlikely to be fatal. According to the Washington Post, there are only an average of 7 yearly deaths in the United States due to spiders.
Black widows have the most toxic bite of any spider in the U.S. They can not only cause intense localized pain, but in some cases a systemic reaction resulting in muscle cramps, high blood pressure, sweating, and nausea.
Female black widows are shiny, black spiders with a leg span that average 1.5 inches in length. Females are larger than males and are the only ones that have a dangerous bite. Female black widows have the characteristic red hourglass marking on the underside of the abdomen. Black widows make irregular, messy webs in dark, secluded areas. These areas may include tall grass, wood piles, basements, storage areas, or any area with clutter. They are nocturnal creatures and like to hang upside down in their webs.
The brown recluse is common in the American midwest and south. Like the black widow, recluses also have a dangerous bite that can cause nausea, vomiting, localized pain, and necrosis (death) of the surrounding tissue.
Brown recluses are light brown or yellowish in color with a dark violin shape on their back. This gives it the nickname of “fiddle-back” spider. They are not very large spiders and their body usually ranges from 6-20 mm long. Other completely harmless spiders like grass spiders and wolf spiders get confused for brown recluses. There are a few ways to tell them apart. Brown recluses are somewhat unique in the spider world because they only have 6 eyes (3 pairs) instead of the more common eight. You can also tell them apart from other look-alikes because their legs are a uniform brown color with no stripes or spots. They live in storage areas, kitchen cabinets, basements, sheds, and other dark areas.
Other Common Species of Spiders
While you may be concerned about poisonous spider bites, the vast majority of spiders are harmless to humans. Aside from them being creepy to some people, the following spiders are very common around homes and yards and are nothing to worry about.
Common House Spider
Identification: These spiders are yellowish-brown with a long abdomen. They are approximately 2.5 cm long with the legs included.
Habitat: In homes they are found in high corners, closets, basements, and garages.
Other: Common house spiders are particularly attracted to lights where insects are present.
American house spider by Judy Gallagher [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Identification: Grass spiders are brownish or grayish with light and dark stripes by the head. They are approximately ¾” long on average.
Habitat: They are found in tall, grassy areas with webs that are usually built near the ground.
Other: Grass spiders use funnel-shaped webs to catch prey and can run fast.
Grass spider By Judy Gallagher [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Identification: Wolf spiders are dark brown with lighter colored stripes on the back. They also have long legs. They range in size from about ½”-1” long.
Habitat: They are found near ground level, often in firewood, leaves, rocks, and debris.
Other: Wolf spiders do not use webs, but instead chase down their prey. There are more than 100 different species of wolf spiders in North America.
Wolf Spider By Mhalcrow [Public domain], from Wikimedia Commons
Identification: Jumping spiders have short legs and thick bodies when compared to many other spiders. They are most often black with lighter colored markings.
Habitat: When indoors, jumping spiders like to hunt for prey around window and doors. When they are outdoors, they can be found on tree bark, under stones, on fences, and in piles of debris.
Other: Jumping spiders are active during the daytime, which is unusual for most spiders.
Jumping spider By Kaldari [CC0], from Wikimedia Commons
Spider Prevention Techniques
Spiders go where there is plenty of food, water, warmth and secluded hiding spots. If you want to keep them away from your home, it is important to eliminate these things through sanitation efforts and sealing the exterior of your home. The following are some useful tips and tricks to prevent spiders.
Keep Your Home Clean
It is impossible to have a perfectly clean home all the time, but eliminating food crumbs and other debris through a regular cleaning routine is key in pest prevention.
- Wipe down surfaces after meals and take out the trash daily so you don’t attract insects
- Vacuum regularly to pick up spider eggs
- Take down spider webs using a broom or a vacuum hose
- Declutter your home and yard to get rid of piles that create hiding places
Seal the Exterior of Your Home
- Seal small cracks and crevices with caulk
- Use expandable spray foam to seal larger holes and gaps
- Ensure that window screens are tight-fitting and free of holes
- Cover vents, chimneys, and other openings with a fine mesh
- Put weather stripping around windows and doors
Change Outdoor Lighting
Insects are attracted to light, and spiders are attracted to insects. Outdoor lighting tends to be a problem because lights are usually around doors, which makes it easy for insects to get inside. To help control insects and spiders, you can change out your old bulbs for yellow LEDs, which tend to attract less insects. You can also move the lights as far away from the door as possible.
Methods of Spider Control
Traps for spiders are typically used more as monitoring devices than as a complete control method. They can help you identify the kinds of spiders around your home and alert you to increases in population. Sticky traps work best when placed in corners where there has been a lot of spider activity. Some traps have lures that draw out insects, because where there are insects, you will find spiders. Harris Spider Traps are a great option.
When using an insect fogger, it is very important to follow all directions. These are usually labeled for use indoors, and will kill flies, mosquitoes, cockroaches, spiders, and other bugs. If you have a large number of bugs that need to be taken care of, a fogger is a fast, easy start. That being said, they do not penetrate deep cracks and crevices very well, so many of your hidden pests may not be affected.
One of the most effective methods of spider control involves a perimeter treatment using a residual pesticide. Wettable powders or microencapsulated insecticides are long lasting and will keep bugs and insects out for months. They can be sprayed around the entire perimeter of your home to form a barrier.
Contact Sprays and Aerosols
Another very effective method for spider control is the use of a contact sprays. These insecticides kill on contact and can be sprayed in hard to reach areas like inside cracks or gaps.
Harris Spider Killer is labeled for indoor/outdoor use and is odorless, non-staining, and long-lasting.
A great long term approach is to use diatomaceous earth as a crack and crevice treatment to control spiders. Long lasting, this technique will continue to work as long as it remains dry.
Your Pest Control Experts
If you are dealing with spiders or other pests, you can take back control of your home with the help of some great Harris products. Harris has been a leader in home pest control products for decades and is America’s oldest EPA registered pest brand. You can trust Harris to deliver the best, safest, most effective pest products on the market.