order
                        
                      
                                    Coleoptera
                                       “Adult Beetles”
                                  
                                    Coleoptera
                                       “Larval Beetles”
                                  
                                    Diptera
                                       “True Flies”
                                  
                                    Ephemeroptera
                                       “Mayflies”
                                  
                                    Hemiptera
                                       “True Bugs”
                                  
                                    Lepidoptera
                                       “Aquatic Caterpillars, Snout Moths”
                                  
                                    Megaloptera
                                       “Alderflies, Dobsonflies, and Fishflies”
                                  
                                    Odonata
                                       “Dragonflies and Damselflies”
                                  
                                    Plecoptera
                                       “Stoneflies”
                                  
                                    Trichoptera
                                       “Caddisflies”
                                 family
                        
                     Psephenidae
               
            genus
                     Psephenus
            
                  “Water Pennies”
               
      Genus Overview
                  
               
                        The larvae of this genus are aquatic. They are almost always found stuck (suction-cup-like) to the sides and tops of rocks, where they feed by scraping periphyton and other food off the substrate. They are very distinctive, flat, shield-shaped larvae, almost trilobite-like in appearance, with the legs only visible from the ventral side Psephenus and Ectopria are the two most common genera in Psephenidae, and can be easily confused, however, they can be readily separated by the presence of abdominal gills ventrally on Psephenus.
                  
               Characteristics
                  
               POLLUTION TOLERANCE
                        Southeast: 2.5 and higher
                                 Upper Midwest: 4 and higher
                                 Midwest: 3.5 and higher
                              0 = least tolerant, 10 = most tolerant
                        FEEDING HABITS
                        
                                 Scraper / Grazer
                        
                     MOVEMENT
                        
                                 Clinger
                        
                     DISTRIBUTION
                        
                                 Widespread (east of the Rocky Mtns.)
                        
                     HABITAT
                        
                                 Lotic-erosional
                        
                     Diagnostic Characters
               order
                         
                                       
                                       
                                    Eye Spots
                                  
                                       
                                       
                                    Lateral Gills USUALLY Absent
                                  
                                       
                                       
                                    USUALLY 4-5-Segmented Legs
                                 family
                         
                                       
                                       
                                    Flat Body
                                  
                                       
                                       
                                    Shield-Like
                                 
                  + Expanded Character List
                  
                     
               
            
                        Order:
                           Larvae: Usually without lateral abdominal gills. If gills present, then 4 hooks clustered on segment 10. Thoracic legs each usually with 4 or 5 segments and with 1 or 2 claws; if without legs, head distinctly sclerotized and posterior body (thorax and abdomen) simple, without gills, hair brushes, suckers, or breathing tube. Eye spots usually present, but compound eyes absent.
                     
                     
                        Family:
                           Short 2–3 segmented antenna. Labrum and clypeus separated by suture. Legs (visible ventrally) 3–4 segmented with only single tarsal claw, suitable for walking. Abdomen 9-segmented. Abdominal tergites without dorsal lobes. Body dorsoventrally flattened, with thoracic and abdominal tergites expanded laterally, collectively forming thin shield covering head and legs from above.
                     
                     
                        Genus:
                           Ventrally, abdomen with 5 paired tufts of thread-like gills. Lateral expansions of each abdominal segment fitting together tightly at margin, but segment 8 without lateral expansions. Abdominal segment 9 without small ventral flap-like lid (operculum) closing caudal chamber.
                     
                   
                   
            Dorsal
               Ventral
               


 
                                                
                                             