Spiders are one of the most feared home invaders. 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 much less than you would think - six per decade in the U.S.).
In order to control spiders, there are several things that are important to know. Don't expect perfection in spider control; they are biologically not very receptive to chemical agents and not very cooperative in picking up pesticides. So just spraying alone is not a great defense against spiders. As you know, spiders are built high off the ground. They don't drag their bellies across surfaces. An insecticide residue on the surface only touches their feet. (Yes, they have feet.) But there's not a circulatory system that will take the insecticide to the organs within the body to cause a quick death. That kind of contact won't cut it for good spider control.
You really have to make contact with the insect via a direct spray, a newspaper, a shoe, or whatever weapon of choice. Spiders are arachnids, not actually insects. True insects such as ants, roaches and wasps, use their mouth to groom themselves habitually, like cats. Spiders don't routinely use their mouth parts to clean themselves. They will clean their legs if there is a large particle stuck to one, 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 we in the pest control industry refer to effective spider control as a "contact kill."
One exception: if you treat the surface of a crevice, a tight squeeze that a spider goes in and out of, like between a baseboard and the carpet, or a piece of wood trim around a window where it meets up with the interior sheetrock or the exterior siding. In these cases, the spider will likely contact his body with the spray when he squeezes in and out of his hiding place.
Methods of Spider Control
An effective approach to spider control is to use the knowledge that they are predators; they primarily consume other insects. So if you can reduce the other insects around your home, spiders will be less interested in hanging around. Most spiders like to hang out near light sources, as they rely on flying insects that instinctively move towards light. A web-spinning spider worth his salt will let his meals come to him. In addition to web-making spiders, there are hunting spiders. They are athletic and really do run down 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.
The best way to control running and jumping spiders at home is to control their food sources around the house - again, 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 a bug stuck in the glue trap. They may be cued visually by this. As a Pest Management Professional, I often see a glue trap with a bug in the glue with a spider stuck right on top of it.
The sticky trap, or glue trap, just captures them - if they walk through the trap, they die. The disadvantage is that you cover less surface area with a trap. 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 traffic patterns for spiders.
Glue traps can also point you towards the source of the infestation - how they are getting into the house. If you have 6 spiders trapped on the right hand side of a glue trap, then look toward the right, along the wall, and look for an opening like a door or wall socket. Perhaps it's a crack that you can caulk.
But one good point about spiders is that they are basically 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 you're often just as effective whacking a spider with a shoe or a newspaper as you would be to spray for them.