The spiders body segments are fused into two tagmata (joined body parts), the cephalothorax (fused head & thorax) and the abdomen. These are joined by a small cylindrical pedicel.
Spiders do not have muscles. They use a fluid movement / hydraulics to move their legs.
Spiders have eight legs and a pair of chelicerae. Chelicerae are the mouthparts, or fangs, that are used to hold and crush prey, or to inject venom. They do not have antennae like insects do.
Spiders have millions of fine hairs on their body called trichobothria. These are critical to the survival of the spider, as spiders do not have ears. The hair is very sensitive and can sense vibrations and movement down to one ten billionth of a meter. Human speech can be detected from several meters away.
Spiders do not have a ¨brain¨ in the way that humans define a brain in the study of anatomy. They do however have a concentration of neural cells that fill up most of the space in the cepholathorax. Some active hunter spiders show signs of intelligence in their choice of tactics and ability to develop new tactics when hunting.