Only three species of the Heligmosomidae are common in France. Heligmosomoides laevis, a parasite of Microtus arvalis, Heligmosomoides polygyrus polygyrus, a parasite of Apodemus spp. and Mus musculus, and Heligmosomum mixtum, a parasite of Clethrionomys glareolus. The morphogenesis of these three species is studied in their respective natural hosts. The larval morphogenesis does not confirm the current phyletic position of the adults, since the synlophes of Heligmosomoides laevis and Heligmosomum mixtum fourth stage larvae are similar and differ from those of Heligmosomoides polygyrus polygyrus and Heligmosomum yamagutii. Therefore, the two genera, Heligmosomoides (longitudinal ridges) and Heligmosomum (oblique ridges on at least one quarter of the body), are very closely related. The subdivision of the genus Heligmosomum into two subgenera cannot be accepted since the type species of Pseudoheligmosomum was not identified correctly: in fact, Heligmosomum mixtum sensu Asakawa and Satoh, 1987 is not the species as described by Schulz (1954). We propose to name it Heligmosomum asakawai n.sp.