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
                        
                     Elmidae
               
            
                  “Riffle Beetle Larvae”
               
      Genus Overview
                  
               
                        33 species in North America.  Most commonly found representative of the Elmidae family.  They have a range of habitats, mostly found in gravel in riffle areas but some are located on vegetation along the banks of rivers.  When in flight, the adults are attracted to lights.  
                  
               Characteristics
                  
               POLLUTION TOLERANCE
                        Southeast: 5.4 and higher
                                 Upper Midwest: 5 and higher
                                 Midwest: 3 and higher
                                 Mid-Atlantic: 5 and higher
                              0 = least tolerant, 10 = most tolerant
                        FEEDING HABITS
                        
                                 Collector / Gatherer
Scraper / Grazer
                        
                     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
                         
                                       
                                       
                                    Brown, Sclerotized, Spindle-Shaped Body
                                  
                                       
                                       
                                    Operculum
                                 
                  + 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:
                           Labrum and clypeus separated by distinct suture. Antennae 2–3 segmented. Head with ocelli in groups of 5. Legs adapted for walking, sometimes small, each 3–4 segmented and with single claw. Thoracic tergites clearly defined. Abdomen 9-segmented, ventral gills absent from segments 1–8. Segment 9 (posterior-most segment) with ventral lid-like flap (operculum) concealing thread-like gills and pair of hooks. Body strongly sclerotized (hardened), dark brown or red-brown, roughly cylindrical or spindle-shaped, with head and legs visible in dorsal view.
                     
                     
                        Genus:
                           Characteristics of the genus:
Posterior sternum of prothorax sclerotized.
Anterior margin of head with two distinct teetth
                  Posterior sternum of prothorax sclerotized.
Anterior margin of head with two distinct teetth
 
                   
            Lateral
               Ventral
               


