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
               
            Optioservus
            
                  “Riffle Beetles”
               
      Genus Overview
                  
               
                        This is a widespread genus with 13(15) North American species (including formally Promoresia). Larvae and adults live in fast and slow portions of streams, clinging to substrate. Adults are collectors-gatherers of fine organic particles.
                  
               Characteristics
                  
               POLLUTION TOLERANCE
                        Southeast: 2.7 and higher
                                 Upper Midwest: 4 and higher
                                 Midwest: 2.75 and higher
                                 Mid-Atlantic: 4 and higher
                              0 = least tolerant, 10 = most tolerant
                        FEEDING HABITS
                        
                                 Collector / Gatherer
                        
                     MOVEMENT
                        
                                 Clinger
                        
                     DISTRIBUTION
                        
                                 Widespread (east of the Rocky Mtns.)
                        
                     HABITAT
                        
                                 Lotic-depositional
Lotic-erosional
                        
                     Lotic-erosional
Diagnostic Characters
               order
                         
                                       
                                       
                                    Elytra
                                 family
                         
                                       
                                       
                                    5-Segmented Tarsi
                                  
                                       
                                       
                                    Big Claws
                                  
                                       
                                       
                                    Last Tarsal Segment 
                                  
                                       
                                       
                                    Thread-like Antennae
                                 genus
                         
                                       
                                       
                                    Epipleura
                                  
                                       
                                       
                                    Prosternal Process
                                  
                                       
                                       
                                    Tomentum of tibia
                                 
                  + Expanded Character List
                  
                     
               
            
                        Order:
                           Adults with hardened forewings (elytra) covering the hind wings. 
                     
                     
                        Family:
                           Terminal segment of each antenna no longer than combined length of 2 preceding segments; antennae thread-like. Elytra concealing entire abdomen or exposing only part of 1 tergite. Each leg with 5 tarsal segments, last tarsal segment about as long as other segments combined and with big claws. Abdomen with 5 visible segments.
                     
                     
                        Genus:
                           Antennae filiform, 10-11 segmented. Pronotum with lateral serrations, small teeth on basal margin, and short longitudinal basal carinae. Foretibiae each with fringe of tomentum. Tarsal claws not unusually long or prominent. Hind coxae transverse. Pair of teeth arising from lateral margins of abdominal sternum IV clasping their respective epipleura of the elytra. Posterior margin of prosternum process narrower than head.
                     
                   
                   
            Dorsal
               Ventral
               


