flatworms, Stimpson, 1857

Luna, Manuel De & Boll, Piter Kehoma, 2023, An annotated checklist of terrestrial flatworms (Platyhelminthes: Tricladida: Geoplanidae) from Mexico, with new records of invasive species from a citizen science platform and a new nomen dubium, Zootaxa 5297 (4), pp. 518-532 : 529

II. Key to subfamilies and tribes of North American terrestrial flatworms

The following key considers only the subfamilies and tribes of species that have been recorded in continental North America, as they are the most likely to be collected in the region. However, one should consider that terrestrial flatworms are regularly being introduced all over the world, therefore, a quick check of the rest of the taxa could prove beneficial while examining specimens. Histological characters, which can only be observed in transverse sections of prepared specimens, are given in brackets.

1 Head laterally expanded into a headplate, conspicuous ( Fig. 27 )..................................... BIPALIINAE

- Head narrow and inconspicuous ( Fig. 28 ).................................................................. 2

2 Body subcylindrical, sometimes showing transverse striae in live specimens ( Fig. 29 ); paired eyes at each side of the head ( Fig. 30 ); [longitudinal cutaneous muscles arranged into a single layer, never in bundles] ( Fig. 32 )......... MICROPLANINAE

- Body flat or subcylindrical; eyes either paired ( Fig. 30 ) or multiple ( Fig. 31 ); [longitudinal cutaneous muscles arranged into bundles] ( Fig. 33 )..................................................................................... 3

3 Eyes numerous, arranged in two or more rows, some of which can extend to the dorsum; [testes located dorsally] ( Fig. 34 )............................................................................. GEOPLANINAE : Geoplanini

- With either paired eyes, or numerous eyes arranged in a single row which rarely extends to the dorsum; [testes located ventrally] ( Fig. 35 )....................................................................... RHYNCHODEMINAE : 4

4 Eyes paired, relatively large................................................................. Rhynchodemini

- Eyes multiple, arranged in a single row or clustering, often inconspicuous.............................. Caenoplanini

Figures

FIGURES 27–35: Visual guide to the key to subfamilies and tribes of North American terrestrial flatworms: (27) laterally expanded head of Bipaliinae; (28) inconspicuous head of most other groups; (29) specimen of Microplaninae with transverse striae; (30) aspect of the head of species with two eyes; (31) aspect of the head of species with multiple eyes; schemes of the cutaneous muscles as seen in transverse sections, with longitudinal muscles simple (32) or arranged into bundles (33); schemes showing the dorsal (34) or ventral (35) position of the testes as seen in transverse sections, with the intestine (dashed outline) as reference.