Almost every insect order has some aquatic representatives. With today's interest in aquatic insects as ecological indicators, insects are very important to all students of aquatic ecosystems. Aquatic environments can be perilous places to live, yet North America has over 5,000 insect species that are especially adapted for an aquatic lifestyle. Some of these insects are adapted to live on the surface of the water, some live in or on the vegetation, others live in open water, and still others are found in the roots or sediment on the bottom. The underwater environment provides everything aquatic insects need to survive, including food and oxygen.
Some insects breathe with fish-like gills and use oxygen dissolved in the water.
Other insects use breathing tubes like snorkles to get their air from above the water. Still others have plastrons, special air bubbles that act like scuba tanks but never need to be refilled. There are striking similarities in feeding habits between aquatic insects and many terrestrial organisms. Some caddisflies spin underwater nets that ensnare prey like a spider's web. Immature dragonflies and damselflies have special mouth parts that flick out like a frog's tongue to catch prey.