Find arachnids information at Animal Diversity Web
Arachnids are spiders, harvestmen, mites and ticks, and their relatives like scorpions that don't live in Michigan. All arachnids have eight legs, and unlike insects, they don't have antennae. The bodies of arachnids are divided into two sections, the cephalothorax in front and the abdomen behind. Sometimes times small arachnids like mites and harvestmen have the two sections fused close together so you can't see the separation. No arachnids have wings, although some spiders can float on the wind using long strands of silk. Many arachnids use silk, either to catch prey or to help them reproduce. Arachnids lay eggs, and have simple development where babies look like small adults and just get bigger as they grow. Some arachnids, especially the mites, change a lot in different stages of their lives. Arachnids are part of a larger group called arthropods, which also includes insects, myriapods, and crustaceans. All arthropods have an exoskeleton and legs that are jointed (arthropod means "jointed foot"). In order to grow, arthropods must shed their whole exoskeleton all at once; this is called "molting."
There are hundreds of thousands of species of arachnids. Arachnids are found in nearly all land habitats, and there are some in aquatic habitats as well. Most arachnids can only eat liquid food, not solid food, so they squirt digestive chemicals into their prey and suck out the juice. Arachnids are predators on insects and other invertebrates, except for many mites, which feed on all kinds of things, like fungus, plants, dead animals, bacteria, and other invertebrates.