The main department of arthropod animals has the class of the arachnids – in addition to the insects – to which, in addition to spiders, scorpions, mites and ticks belong as well. A conspicuous difference with the insects, is that all arachnids have eight legs. Insects have just 6 legs. In spiders, the head and the thorax are grown together. The abdomen is covered with soft skin and contains spider nipples. Just like insects, spiders have an exterior skeleton, the chitin skin; during growth, they moult several times. In the head, there are two feelers and two large, strong jars with point poison claws through which a channel runs through the poison glands. When the spider bites, the poison is pressed into the body of an insect or mite etc via the channel. For humans, the bite of the spider species in the Netherlands is harmless. They are harmless for goods and materials; the only nuisance spiders cause is the webs they make. The spider species that live in the Netherlands reach a maximum age of about a year. Several species overwinter and die in the fall.
The most well-known species are the wheel spiders, named after the wheel-shaped web they make to catch their prey. Other spider species catch their pray with funnel, tube or hammock shaped webs. Other species make a chaos of webs or simply tripwires. The web spiders catch their prey using a web, and remain at that location until the prey stops by. The simpler the web construction, the more active a hunter the spider is. The true hunters don’t use a web to catch their pray, but sneak up to or hunt their prey. The fairly large wolf spiders in particular are fierce hunters that can walk really fast. The jumping spiders approach their prey up to inches and then jump them.
Spiders are useful because they often capture harmful or annoying insects, such as flies and mosquitoes, but also larger insects, such as grasshoppers, beetles and wasps and should therefore be left alone. Spiders usually walk, but they can also float on the threat they create. This allows them to move dozens of meters through the air.
If large numbers of spiders live in the garden or house, this may be a clue that a lot of prey (flies, mosquitoes) live there. To prevent a plague of this prey, it is wise to allow the spiders to do their work. There’s no use trying to eliminate the prey outdoors, because the many insect species can come from everywhere. Their breeding places are everywhere, depending on the species, on trees and plants, in the soil, in grassland or soggy terrain etc.
The number of eggs dropped by spiders varies from several to almost a thousand. They involve in breeding care. The web spiders usually make a cocoon in which they deposit the eggs. In the hunters, the female carries the cocoon until the young spiders have hatched, and sometimes even a little longer. Sometimes, one finds a lot of young spiders in the house, which have then crawled from a cocoon which was dropped in the house.
Spiders an insects can hide or gain access to the house via open windows or doors and via cracks between notches and window frames and the masonry, or via ventilation ducts that are too big. To prevent the spiders and their prey from invading the house, one must repel them by sealing cracks with sealant, sealing ventilation ducts with a solid roster or fine mesh. Properly closing fly screens can be applied to the windows and doors. Eliminating spiders is undesired and the use of pesticides is ill-advised. Webs can be removed with a tousle or the vacuum cleaner. The spiders inside the house can be captured, with a glass and a firm piece of paper which is shoved under the opening for instance, after the caught spider is released outdoors.