VETERINARY MEDICAL IMPORTANCE
Subclass Digenea
1a. Dioecious (separate sexes) ......................................................................................................... Schistosomatidae
1b. Monoecious (hermaphroditic) ................................................................................................................................ 2
2a. Ventral sucker posterior-terminal or posterior-subterminal ................................................ Paramphistomatidae
2b. Ventral sucker central or anterior of center ......................................................................................................... 3
3a. Body constricted into two portions, third holdfast (tribocytic organ) present ...................................................... 4
3b. Body without a midline constriction ........................................................................................................................ 5
4a. Forebody cup-shaped, auxilary holdfast lobed ........................................................................................ Strigeidae
4b. Forebody spatulate-shaped, third holdfast oval, two anterior-lateral auxillary suckers ................ Diplostomidae
5a. Body less than 2.0 mm long ..................................................................................................................................... 6
5b. Body greater than 2.0 mm long ............................................................................................................................... 8
6a. Body sac-like Vitellaria globular, numerous and scattered throughout ........................................ Nanophyetidae
6b. Vitellaria located in posterior half of body ..............................................................................................................7
7a. Ceca long, extending posteriorly past ventral sucker .................................................................... Heterophyidae
7b. Ceca short, not extending past ventral sucker ............................................................................... Microphallidae
8a. Body thick and football-like; acetabulum and uterus centrally located; vitellaria dense.......... Troglotrematidae
8b. Vitellaria gouped laterally and posterior to ventral sucker ................................................................................... 9
9a. Head with a collar armed with thick spines ................................................................................ Echinostomatidae
9b. Head collar and spines absent ................................................................................................................................10
10a. Ovary posterior to testes; uterus first descends then ascends ....................................................... Dicrocoelidae
Dicrocoelium and Platynosomum
10b. Ovary anterior to testes ....................................................................................................................................... 11
11a. Ovary central; testes larteral to ovary; uterus first descends then ascends .......................... Prosthogonimidae
Prosthogonimus
11b. Ovary and testes in linear tandem arrangement; uterus ascends only ............................................................. 12
12a Body long, (1-4 inches) wide (1/2-1 inch) and leaf-like; anterior end cone-shaped or rounded ......... Fasciolidae
Fasciola Fascioloides Fasciolopsis
12b. Body narrow and tapered toward anterior end ............................................................................... Opisthorchiidae
Opisthorchis or Clonorchis
