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
                        
                     Heptageniidae
               
            Maccaffertium
            
                  “Flat-headed Mayflies”
               
      Genus Overview
                  
               
                        There are at least 16 species with larvae found in both fast and slow lotic (flowing water) habitats of North America. Fly fishers know the duns of various species as "March Browns" and "Light and Dark Cahills." Larvae are clingers in these streams and feed primarily as scrapers of attached algae, diatoms, and other biofilm, although they may simply collect fine organic particles facultatively.
                  
               Characteristics
                  
               POLLUTION TOLERANCE
                        No pollution tolerance ranges defined.
                        FEEDING HABITS
                        
                                 Collector / Gatherer
Scraper / Grazer
                        
                     Scraper / Grazer
MOVEMENT
                        
                                 Clinger
                        
                     DISTRIBUTION
                        
                                 Widespread (east of the Rocky Mtns.)
                        
                     HABITAT
                        
                                 Lotic-depositional
Lotic-erosional
                        
                     Lotic-erosional
Diagnostic Characters
               order
                         
                                       
                                       
                                    Abdominal Gills
                                  
                                       
                                       
                                    Single Tarsal Claw
                                  
                                       
                                       
                                    Usually 3 Tails
                                 family
                         
                                       
                                       
                                    Flat Head And Body
                                  
                                       
                                       
                                    Margin Around Eyes
                                 genus
                         
                                       
                                       
                                    Gills On 1–6 Truncate
                                  
                                       
                                       
                                    Gills On 7 Slender
                                 
                  + Expanded Character List
                  
                     
               
            
                        Order:
                           Wings developing in wing pads. Mouthparts suitable for chewing. Gills present on tops and sides of abdomen. Segmented legs present. One tarsal claw per leg. Usually with 3 tails (sometimes 2).
                     
                     
                        Family:
                           Head and body dorsoventrally flattened (depressed). Eyes and antennae positioned dorsally. Lateral margins of head visible beside the eyes. Mandibles not visible from dorsal side. Claws much shorter than tarsi. Tibiae and tarsi straight. Abdominal gills on segments 2–7 variably shaped depending on genus and species.
                     
                     
                        Genus:
                           Maxillary palps rarely protrude at sides of head. Second segment of each maxillary palp is short and inconspicuous. Gills on abdominal segments 1–6 have truncated distal ends, each with at least part of apical edge straight. Fibrilliform portion of gills on abdominal segments 2–6 each with many conspicuous filaments. Gills on abdominal segments 4–6 positioned laterally, and usually with broad lamellae (flat plate-like portion of gills). Gills on abdominal segment 7 reduced to slender filaments, and trachea absent or with few or no lateral branches. Posterior end of abdomen with three well-developed tails.
                     
                   
                   
            Dorsal
               Ventral
               


 
                                                
                                             