Males use their jaws to fight over females. Females lay hundreds of fertilized eggs above the water on low-hanging branches or plants. Larvae hatch and drop into the water. They are found hanging around vegetation near moving water, while adults can be found resting on dwellings nearby.
Activity is mostly seen at night during the late spring and throughout the summer. Adult Fishflies pull aquatic insects (naiads of dragonflies, water beetles, etc,) out of the water and eat them. They will also eat worms, small bivalves (clams, mussels) and algae. Adults are very drawn to lights at night.