Intraspecific variability was studied in Clarkus papillatus (Bastian, 1865) Jairajpuri, 1970 with the help of a Benzecri's factorial analysis of correspondences. Body shape and size can vary according to the type of humus in which the nematodes are living. Two morphometric characters (body and tail lengths) can be used to distinguish populations, thus like the other mononch Prionchulus punctatus, Clarkus papillatus can be considered as a good indicator of humus type differentiation. A seasonal variability also was demonstrated in several biotopes representative of each investigated humus type. Environmental and nutritional influences upon morphometric characters have been discussed.