These alderflies are small and mainly brown with a relatively heavy body and forewings reaching a length of 10 to 20 millimeters. Females are usually larger than males. They have wings with large cells forming a network. The upper edge of the front wings consists of almost square cells. The species belonging to the genus Sialis have less than fifteen square cells, while the other Megaloptera have more cells. The adults are diurnal and fly from May to June on the riparian vegetation.
