Megalopterans begin their lives hanging over water. Females lay egg masses on leaves, branches, or other surfaces over ponds and streams. When the larvae hatch, they fall into the water. Megalopteran larvae fend for themselves immediately, taking shelter under rocks or sand. The larvae are important members of aquatic food webs, feeding on worms and other insect larvae and preyed upon by fishes and other aquatic predators. It takes a few years for Megalopteran larvae to grow up, and they shed their skin (molt) each time they get too big for it. When at their adult size, they crawl out of the water. They pupate inside burrows under soil or dead leaves on the shoreline. Within just a few days, metamorphosis occurs, and a winged adult megalopteran emerges. The adults live just a few hours or, at most, a few days, during which they don't eat but do try to mate.

Insects are the only animals without backbones (invertebrates) that can fly. Wings of insects are flat and paper-thin, supported by a network of veins. They flap their wings at incredible rates, up to about two hundred times per second. Most insects have two sets of wings that work in tandem because they are coupled by a fold, a hook, or other structure that catches the back wing as the front wing beats. Wings are made of two layers of cuticle for strength. The front wing is often hardened to serve as a protective cover, leaving the back wing to provide most of the flying power. Many insects walk around instead of, or in addition to, flying. The good walkers tend to touch three legs to the ground at a time, alternating with other sets of three (tripedal gait). The stable triangles formed by the legs allows them to move quickly without falling over. Some insects "walk" on water or swim.