Small Square-Gill Mayflies
These photos supplement pages 49-62 of the Guide to Aquatic Invertebrates of the Upper Midwest. Information on the biology of Caenidae can be found on page 57. Be careful to look at the shape of the gill. Caenidae gills are square and nearly or absolutely touching along the midline. Tricorythidae gills are triangular or oval and do not touch at the midline. Click to compare with Tricorythidae.