1. Filiform worm 1-2 mm in length. . . . . . . . . . . . . . . . . . . . . . . . . Nematoda
Filiform worm 10 to 70 cm in length, diameter 0.3-2.5 mm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nematomorpha, 2
2. Cuticular areoles absent in one or both sexes, if evident, simple and weakly defined elevations only, polygonal or ovoid; bilobed posterior of male with a transverse cresent just anterior of cloaca. . . . . . . . . . . . . . . . Gordius sp.
Cuticular areoles, simple or complex, present and well defined; without a crescent on posterior ventral surface of male. Posterior with elongate lobes, if bilobed with rows of tubercles on either side of cloaca, or posterior (female) with three lobes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Paragordius varius