Spiders, scorpions, lice, and ticks belong to this class.  Segmentation varies in different arachnids.  Arachnids posses eight legs and most are carnivorous.  Most have claws, fangs, poison glands and stingers.

The spider body is divided into two segments.  The head and the thorax are fused (cephalothorax) and the abdomen.  In mites and ticks, the segments are fused together and the body appears un-segmented.

In scorpions the body is divided into a short cephalothorax, a pre abdomen and a post abdomen (tail). 

In mites and ticks, the segments are fused together, therefore the body appears as un-segmented.