Spiders

The house spider is the most common type of comb-footed spider, a group that includes the black widow species. They are urban pests and are common throughout the world, and their webs are most often found in corners, basements, under furniture and around windows. The house spider hangs upside down in its web, which is made up of trip lines that extend vertically and horizontally throughout the web to entrap prey. The web of the house spider is irregularly shaped and has a scaffold-type arrangement. Prey gets caught in the trip lines, which direct it into the centre of the web. It is then killed by a bite and subsequent venom injection.

What do spiders eat?

House spiders mainly prey upon small insects such as fruit flies. Spiderlings construct larger webs as they mature and require more food. Webs are frequently abandoned in sites that do not yield prey, and new webs are constructed. In fact, house spiders are often referred to as cobweb spiders because of the abandoned webs they leave behind.

Why are there so many of them?

The female produces approximately 250 eggs, which are placed in a silken sac in the centre of the web. Under good conditions, depending on temperature and humidity, several egg sacs may be present in the web at the same time. The eggs will hatch after seven to 10 days, and the spiderlings will remain in the silken sac for one moult. After the first moult, the spiderlings emerge from the sac and "balloon" to new locations by spinning silk threads. They can live for 20 days or longer without eating. Consequently, the survival rate of the house spider is fairly high.

Do house spiders do any harm?

No. House spiders are harmless and more of a nuisance than a health risk.

How do I get rid of them?

Because house spiders usually construct their webs in open areas of buildings, the easiest way to manage infestations is by non-chemical methods. Removal is the most effective means of managing an infestation. Spider webs and egg sacs can be easily removed with a vacuum. However, preventative measures should also be taken to ensure that spiders cannot enter structures. Cracks in exterior walls should be sealed, and weather-stripping should be tightly fitted around door frames. Exterior lights attract insects, which, in turn, attract spiders to prey. Therefore, mercury vapour lights should be replaced with sodium vapour lights, which are less attractive to insects. Also, exterior lights should only be used when needed.