These photos supplement pages 77-86 of the Guide to Aquatic Invertebrates of the Upper Midwest. Information on the biology of Pteronarcyidae can be found on page 86. There are 2 families of Stoneflies that have gills on their thorax: Pteronarcyidae and Perlidae. Pteronarcyidae has gills on abdominal segments 1 and 2 as well as the thorax, whereas Perlidae has gills only on the thorax. Click to compare with Perlidae.