Thoracic notum is fused and covers first 5 abdominal segments
Gills are usually concealed by thoracic notum
The larvae of Baetiscids have a unique and bizarre appearance due to the enlarged thoracic notum and often the presence of large spines. Larvae and adult range from 4-14 mm in length. Members of this family are considered collector/ gatherers and inhabit pools or runs in sandy streams. Baetiscids swim by tucking their legs under their body and undulating their abdomen and caudal filaments.
Merritt, R W., K W. Cummins, and M B. Berg. An Introduction to the Aquatic Insects of North America. Dubuque, Iowa: Kendall/Hunt Company, 2008.