Arachnids are a type of arthropod. You know many of them as spiders.
Like other arthropods, the arachnids have a hard exoskeleton and jointed
appendages for walking. Unlike other arthropods, arachnids do not have
antennae. Common arachnids are the spider, scorpions, ticks and mites.
Spiders have 8 appendages. The first pair are used for holding the
prey and feeding. The second pair may also be used for holding and killing
their prey.The others are used as legs for walking. Most spiders also have
8 eyes. Spiders have fangs that are used to inject poison to paralyze or
kill their prey.
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 8 inches in
length. They have 6 to 12 appendages. They also have a sharp stinger at
the end of their tail which is sed 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.