Most anglers need a basic understanding of insects when fly fishing for trout. You do not need to spout out Latin names or describe detailed lifecycles. However, it is important to know the differences between a nymph, an emerger, an adult, a terrestrial, and the various other types of foods trout may eat. A nymph is the larval or pupa stage of an insect’s life. Nymphs live in a river year-round and will hatch or emerge into adults. An emerger is a nymph that is in the process of changing from an insect that lives in the water to one that will live out of the water. An adult are the insects most anglers see when fishing—they are the dry flies that are fluttering on the surface of the water or clinging to rocks or streamside vegetation. Terrestrials are any insects that normally live on land and my crawl, be blow, or land in the water. Because most trout are opportunistic, trout will eat all sorts of other foods including, but not limited to, smaller trout, other smaller fish, salamanders, newts, small rodents, and perhaps the occasionally baby duck.