MACROINVERTEBRATES are animals without a backbone that can be seen with the naked eye. These bottom-dwelling animals include crustaceans (crayfish, mussels, snails) and worms but most are aquatic insects. Beetles, caddisflies, stoneflies, mayflies, hellgrammites, dragonflies, true flies, and some moths are among the groups of insects represented in streams. Macroinvertebrates are an important link in the food web between the producers (leaves, algae) and higher consumers such as fish.
View a guide to Freshwater Macroinvertebrates at STROUD Water Research Center
SLUG Gastropod mollusc
Slugs are sluggish. They travel four inches a minute, and rest often. Their home territory is at most a few yards square and a slug travels around this area on a mucus highway. Not only does he/she have to protect its soft body from rough terrain, but all the skin of a terrestrial slug must be kept damp to enable the exchange of oxygen. For a slug, your skin is your lungs.