Arachnids are a type of arthropod. The most commonly known type of arachnid is the spider. Like other arthropods, arachnids have a hard exoskeleton and jointed appendages for walking. Unlike other arthropods, arachnids do not have antennae. Common types of arachnids are spiders, scorpions, ticks, and mites.
Spiders have eight appendages. The first pair is used for holding the prey and feeding. The second pair can also be used for holding and killing prey.The others are used as legs for walking. Most spiders also have eight eyes. Spiders have fangs they use to inject poison into their prey to paralyze or kill them.
Many spiders can produce silk threads to spin webs for catching prey and for building cocoons for their eggs.
Scorpions are the largest arachnids, some reaching over eight inches in length. They have six to twelve appendages. They also have a sharp stinger at the end of the tail, which is used to paralyze or kill insects and small animals.
Mites and ticks are small arachnids that are parasites living on the blood and tissue fluid of other animals. They can occasionally transmit disease.