AbstractEgg masses and eggs of Sialis hasta, S. iola, S. joppa, S. infumata, S. aequalis, S. vagans, S. glabella, S. mohri, S. velata, and S. itasca are described using SEM micrographs. Diagnostic characteristics of chorion surface and micropylar structure and a key for specific determination of eggs of these 10 species are given. Oviposition is confined to leaves and twigs near or overhanging water. Eggs are oriented either vertically or horizontally in the egg mass, and hatch in 5 to 10 days in the laboratory. Hatching larvae are aided by an egg burster which tears the chorion and aids in removing the embryonic envelope.