Heterodera thornei n. sp. (Nematoda:Heteroderidae) and a review of related species.

In a taxonomic review of the species of the Heterodera "cacti group," H. thornei n. sp. is described and illustrated from Miner's lettuce in California. This new species is distinguishable especially by havpunctate egg shells and a larval stylet (27 mum) and tail (56 mum) longer than other related species. Heterodera weissi is redescribed, type specimens are designated, and new data added on the basis of original and topotype specimens. New morphometric data, along with illustrations, are given for H. cacti, H. amaranthi, and H. estonica, and certain details in the original descriptions are clarified on the latter two species. Diagnoses and a key for identification of these species are given. A common name for each species is proposed when one is lacking. Previously unrecognized tooth-like structures occurring in the vulval cone top of these species and in H. schachtii are characterized and named "vulval denticles." Because of its markedly different morphology, especially in cysts, H. betulae is removed from the H. cacti group and placed alone, since it is incompatible with any of the present Heterodera "groups." Know distribution of these species is given, with the result that many new areas and countries of occurrence for some of the species are listed.