The family Corydalidae contains the megalopterous insects known as dobsonflies and fishflies. Making up about one dozen genera, they occur primarily throughout the Northern Hemisphere, both temperate and tropical, and South America. The larvae are aquatic, active, armed with strong sharp mandibles, and breathe by means of abdominal branchial filaments. When full sized — which can take several years — they leave the water and spend a quiescent pupal stage on the land, in chambers dug under stones or logs, before metamorphosis into the sexually mature insect.