Baetisca

Baetisca is a genus of mayflies in the family Baetiscidae. They are commonly known as armored mayflies due to the extended mesonotum that covers much of their abdomen, providing a shield-like appearance. Baetisca nymphs inhabit cool, fast-flowing streams and rivers, typically found in riffle habitats with coarse substrates. They are distributed throughout North America.

The nymphal stage of Baetisca is characterized by its flattened body and the large, carapace-like mesonotum. This covering serves as protection from predators and aids in their benthic lifestyle. The gills are located beneath the mesonotum. The adults are short-lived and play a crucial role in the aquatic ecosystem as a food source for fish and other predators. Identifying Baetisca species often relies on subtle differences in the nymphal morphology, particularly the shape and ornamentation of the mesonotum.

Baetisca species are considered relatively intolerant of pollution, and their presence is often an indicator of good water quality. Therefore, they can be used as bioindicators in stream health assessments.