Introduction

Spiders commonly found in Canadian homes include house spiders, wolf spiders, cellar spiders, fishing spiders and, much more infrequently, black widow spiders.

Spiders are usually found in corners of rooms, closets, boxes, dark crevices, basements, garages, and gardens. Spiders are excellent pest controllers. Wolf spiders are especially beneficial to farmers and gardeners because they prey on common crop pests such as cottonworms, gypsy moths and pea aphids. Spiders do not transmit any diseases. Although nearly all spiders have venom glands, they rarely bite humans and only a few species, such as the black widow spider, can have a dangerously venomous bite.

Identification of Household Spiders

The spider has an unsegmented body with two main divisions, four pairs of walking legs and organs for producing silk which is used for making nests, webs to catch prey or cocoons for its eggs. Spiders can have up to eight eyes. With so many eyes, it is surprising that most spiders are near-sighted. Many spiders prey on pests such as flies, mosquitoes, plant hoppers and gypsy moths that get caught in their webs. Once the prey becomes tangled in the web, the spider immobilizes it by wrapping it in more silk and then injecting venom to paralyze it. Later the spider injects a predigestive liquid and sucks out all the nutrients from its prey. Most spiders are nocturnal, shy, and avoid confrontation by running away. They will only bite if squeezed or held.

Wolf Spiders

Wolf spiders are unusual because they do not build webs but rather hunt for their prey. These spiders can be as large as 3 cm in length and are dark brown in colour. They are generally found in grasslands, woodland floors, beaches and gardens.

Cellar Spiders

These spiders have very long legs and build their webs in the corners of cellars or cool, damp basements. Cellar spiders are harmless and can be eliminated by removing the webs and reducing the humidity in that area of the house.

House Spiders and Black Widow Spiders

The house and black widow spider belong to the same family ( Theridiidae ). The house spider is more commonly found within the house whereas the black widow spider is more likely to be found in dark crawl spaces or garages. The black widow spider is shiny black with a distinctive red hourglass-shaped mark on the underside of the abdomen. It spins a small, silk web close to the ground. Its name is derived from the female's tendency to consume the male after mating.

Fishing Spiders

Although fishing spiders resemble wolf spiders they have a different eye pattern. The adults can reach up to 7.5 cm in width. They are commonly found near cottages and waterfronts, especially around rocks near the shoreline. These spiders forage for their prey and the females only spin webs to surround their eggs, which they guard.

Preventative Control of Household Spiders

Keeping your house clean reduces the number of pests that are food sources for spiders. To prevent pests from entering the home, weatherstrip or caulk windows and doors and repair screens. When cleaning your garage or basement or working in your garden, it is advisable to wear gloves to avoid being bitten. Spiders are beneficial; a few spiders left in basements and crawlspaces will help to capture earwigs and other insects.

Physical Control of Household Spiders

• Sweep or vacuum baseboards and corners of rooms frequently to remove any food debris.
• Remove spider webs when spiders are not occupying them.
• Sweep behind washers and dryers regularly and rearrange furniture periodically to avoid spiders spinning webs in the same location.
• Keep clothing, shoes and blankets off the floors so that spiders do not hide in them during the day.
• If there is a spider near a door or window, just sweep or brush it outside.
• You can also trap live spiders with a glass jar and a piece of stiff paper and then release them outdoors.
• If necessary, they can be eliminated by using a fly swatter, rolled-up paper or magazine.
• Use yellow light bulbs outdoors to attract fewer insects, thereby discouraging spiders from spinning webs near the house.
• If you have an outhouse at your cottage, there may be some spiders. Always check to make sure there are no spiders underneath the rim of the seat. Make sure that the outhouse is clean, the door is weatherstripped and closes tightly, and all openings are screened properly.

Chemical Control of Household Spiders

If the infestation of your house or garden is severe enough to warrant the use of pesticides, products containing the following chemicals are registered for controlling most common spiders: pyrethrin, permethrin, carbaryl, piperonyl butoxide, d-trans allethrin, and n-octyl bicycloheptene dicarboximide.

These products can be purchased in hardware or grocery stores and garden centres. They can be applied around the exterior surfaces of window and door frames to prevent entry. There are also products that can be sprayed or painted on interior window and door frames, baseboards, floors, floor coverings, underneath furniture and in closets and crevices. Complete eradication of spiders by chemical means is not advisable because spiders are natural and efficient pest controllers.

Be sure to read Proper Use of Pesticides.