Ephemeroptera (Mayflies)
Family: Baetidae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Procloeon caliginosum | McDunnough, 1925 | Rough-shod small minnow mayfly | pre-1936 | Canada | Missing | Access |
| Procloeon insignificans | McDunnough, 1925 | Insignificant small minnow mayfly | ? | Canada | Missing | Access |
Family: Ephemeridae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Ephemera compar | Hagen, 1875 | - | (rediscovered) | Foothills, Colorado, USA | Rediscovered | Access |
| Pentagenia robusta | McDunnough, 1926 | - | 1926 | Ohio River region, Indiana, Kentucky, Minnesota and Ohio, USA | Extinct | Access |
Family: Heptageniidae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Rhithrogena gaspeensis | McDunnough, 1933 | Mt. Lyall flat-headed mayfly, Quebec flat-headed mayfly | pre-1934 | Quebec, Canada | Missing | Access |
Family: Isonychiidae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Isonychia diversa | Traver, 1934 | Diverse mayfly | 1916 | Tennessee, USA | Extinct | Access |
Family: Leptophlebiidae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Paraleptophlebia brunneipennis | McDunnough, 1924 | - | ? | North America | Missing | Access |
| Paraleptophlebia californica | Traver, 1934 | - | ? | California, USA | Missing | Access |
| Paraleptophlebia clara | McDunnough, 1933 | - | ? | California, USA | Missing | Access |
| Paraleptophlebia placeri | Mayo, 1939 | - | ? | California, USA | Missing | Access |
| Paraleptophlebia rufivenosa | Eaton, 1884 | - | ? | North America | Missing | Access |
| Paraleptophlebia traverae | McCafferty & Kondratieff, 1999 | Grangeville prong-gilled mayfly | 27 June 1907 | Idaho, USA | Missing | Access |
| Tikuna atramentum | (Traver, 1947) | - | (rediscovered) | Costa Rica | Rediscovered | Access |
Family: Oniscigastridae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
|
Oniscigaster intermedius |
Eaton, 1899 | 13 January 1920 | Arthur's Pass, Central Alps, New Zealand | Invalid (synonym) | Access | |
| Oniscigaster wakefieldi | McLachlan, 1873 | - | (rediscovered) | New Zealand | Rediscovered | Access |
Family: Siphlonuridae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Acanthometropus pecatonica | (Burks, 1953) | Pecatonica River mayfly | June 1986 or June 1991 | Illinois (Sugar and Pecatonica Rivers) and Wisconsin (Black and Chippewa Rivers), USA | Missing | Access |
| Parameletus croesus | McDunnough, 1923 | - | ? | Ontario, Canada | Missing | Access |
| Siphlonurus luridipennis | Burmeister, 1839 | - | pre-1840 | North Carolina, USA | Extinct | Access |