Spiders are one of the most-feared of all pests in the home that people want to exterminate. There are more phobias about spiders than any other pest, and understandably so. If you get bitten by the wrong spider - a black widow or a brown recluse - and you have a bad reaction to the venom, you can end up in the hospital. And yes, there have even been some deaths associated with spiders (though fewer than you may think - only six per decade in the U.S.).
There are several things you need to know about pest control and spider prevention:
- Don't expect perfection in spider control. Chemicals are not very effective against spiders, nor do the spiders readily pick up pesticides. So just spraying is not a great defense against spiders. With their long legs, spiders keep their bellies well above the ground, so sprayed insecticide residue on a surface will only touch their feet. But they don't have a circulatory system that will carry the insecticide from the bottoms of their feet to the organs in their bodies that would cause them to die.
- So - you really have to make contact with the insect through a direct spray, a newspaper, a shoe, or whatever is your weapon of choice. Spiders are arachnids, not actually insects. True insects (such as ants, roaches, and wasps), use their mouths to groom themselves, so they end up eating insecticide that gets on their feet, legs, and bodies. But spiders don't routinely use their mouthparts to clean themselves. They will clean their leg if there is a large particle stuck to it, but it's not a habit that will guarantee pesticide will kill them. In addition, most spiders spend their entire lives sitting in webs (a non-treated surface). So, spider control needs to be a "contact kill."
- There is one exception to #2: If you use a pesticide spray on the surface of a crack that a spider goes in and out of, (such as between a baseboard and the carpet, or a piece of wood trim around a window), the spider's body will likely contact the spray and the pesticide could be effective.
- The best way to control running and jumping spiders at home is to control their food sources around the house. Spiders eat other insects, so reducing the other insects around your home will reduce their food sources, and spiders will be less interested in hanging around. Most spiders like to hang out near light sources, which helps them capture flying insects that are attracted to light. A web-spinning spider worth his salt will let his meals come to him; hunting spiders are more athletic—they really do run down their prey. A subcategory of hunting spiders is jumping spiders. If you've seen one of those, you recognize it. They have more of a pouncing behavior to capture their prey. The spiders with short, stubby legs are almost all of the jumping variety. The spiders with long - but not delicate - legs are the running spiders. These include wolf spiders and brown recluse. You won't find those spiders spinning a web.
- So - to get rid of spiders, get rid of your other bugs. Crack and crevice treatment with insecticides provide some control, but you can also use glue boards or sticky traps. These are non-pesticide capture mechanisms. Some can be folded into a box shape so that unintended items won't get stuck to them. There are really no attractants in most of these glue traps. Some companies try to add a scent, but the most attractive thing for a spider is seeing a bug stuck in the glue trap. Pest control professionals often see glue traps with a bug in the glue—and a spider stuck right on top of it.
- The sticky trap, or glue trap, just captures spiders - if they walk through the trap, they die. But you can't cover much surface area with a trap, so you have to place them where the spiders are most likely to come to them. The most effective places to put glue traps are in dark, quiet areas. A closet is a good example, or between a bed and a wall, or by any piece of furniture - these are all common spider travel areas.
- Glue traps also can point you toward the source of the infestation - enabling you to discover how the spiders are getting into the house. If you have 6 spiders trapped on the left side of a glue trap, then look toward the left, along the wall, and check for an opening like gaps around or under a door or non-aligned wall socket. If it's a crack that you can caulk - do so.
- Spiders are that they are essentially loners - they aren't social insects that live in big groups, like ants or bees. As predators, they like to operate on their own and not share their food. So it is often just as effective to whack a spider with a shoe or a newspaper as to spray them. Or try the newest method of spider control with this spider trap: The Spider Catcher - enabling you to grab a spider with a long grabber without getting anywhere near it!
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Spiders, University of California Agriculture & Natural Resources
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Ingley, Spencer J., et al. Social Context, but Not Individual Personality, Alters Immigrant Viability in a Spider with Mixed Social Structure. Animal Behaviour, vol. 120, 2016, pp. 153–161., doi:10.1016/j.anbehav.2016.08.009