All spiders have two body sections: the cephalothorax in front and an abdomen behind. The abdomen contains the digestive and reproductive systems, and on the underside of it are the glands where silk is produced. The structures that produce the silk are called spinnerets.
They have eight legs, all attached to the cephalothorax. On the front of the cephalothorax are the mouth, the fangs, the eyes, and two small "mini-legs" called pedipalps. These are used to grab prey, and in mating, and are much bigger in male spiders than in females. Different species of spiders have six or eight eyes, and the size and arrangement of eyes is different in different groups. All spiders have fangs that they use to bite their prey with, and most have venom glands.
Female spiders are often much bigger than males.
The first thing you look for to identify a possible spider infestation is their webs. The size and shape of these spider webs vary by species and their number can possibly identify the population numbers you might have on your property. Some spider webs are traditional web formation, but some are orb-shaped while others are funnel-shaped. But not all spiders spin webs, so just because you don't see them doesn't necessarily mean you are free from infestation. Some spider species live in burrows, while others are free-ranging and take refuge in crevices.
Spiders can be found in moist environments, and can be found in basements, walls, sheds and other damp locations. They can also be found in attics, the junction of a wall and ceiling, closets and storage boxes.
Like all infestations, a spider infestation starts with an abundance of a food source. Spiders feed on other insects and prey on ants, flies, woodlice and other spiders, so where there is a plentiful supply of other insects, spiders will wait to find their next meal. So, if you have a spider infestation, chances are, you have one or more kinds of insect infestations on your property or in your home.