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It's fun to go swimming in the summertime, but have you ever wondered what it would be like to spend your entire life in the water? What would you do when a spring thunderstorm transforms your stream from a tiny brook into a raging river? Where would you go when a summer drought turns your pond into a desert of caked mud? And how would you survive those cold winter days when the water turns to ice? Aquatic environments can be perilous places to live, yet North America has over 5000 insect species that are especially adapted for an aquatic lifestyle. 
Most of these insects live in moving water (brooks and streams) or near the edges of ponds and lakes where rooted plants can grow (the littoral zone). 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. Food comes from plants or other animals that share the aquatic environment; oxygen may come directly from the water or from the air above it. 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.
The insect life in a pond, lake, or stream often has a significant impact on other organisms in the evironment. Insects are a major part of the diet for many fish and other small vertebrates. Aquatic insects may serve as biological control agents to clear weeds, like the water hyacinth, from commercial and recreational waterways. Marsh flies are parasites of snails and Coelopids feed on seaweeds. Many insects live in the water as immatures and then move to terrestrial habitats as adults. Some of these, like mosquitoes and black flies, spread human diseases in their adult stage. |
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 mouthparts that flick out like a frog's tongue to catch prey. Larvae of mosquitoes and black flies have special appendages that work like a kitchen strainer to filter small particles from the water. These filter feeders help maintain water quality by reducing organic pollutants and microscopic organisms. Some sewage treatment plants are designed with trickle filters that harbor aquatic insects and other decomposers.