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.

An insect has a brain, connected to bundles of nerves (ganglia) in each of its three body segments. Like us, they have sensory nerves that receive information from their environment and send it to the brain. Information comes from many types of touch receptors. Touch-sensitive hairs all over an insect's body are sensitive enough to detect vibrations in the air, such as from an approaching predator. Insect hairs also do chemical detection (chemoreception). Pores at the end of chemoreceptors on mouthparts or other body parts allow odors to reach the nervous system. Insect antennae may have thousands of chemoreceptors, used to detect chemicals in the air (pheromones) emitted by members of the opposite sex. An insect, like us, has a pair of eyes on its head. But, insect eyes are compound, with hundreds or thousands of lenses, together making an image consisting of spots of light, like pixels. An insect's sound receptors are on its legs.