Identification of Heterodera cysts by terminal and cone top structures

Detailed examination of the cysts of 39 of the 53 described species of Heterodera, a cyst-forming nematode, was undertaken to provide an adequate basis for identification of these species. Taxonomic keys, based on information gained from studies of cone top and terminal areas of the cyst, are presented. Five morphologically distinct groups are recognized based on difference in vulval slit length, fenestral length, underbridge structures, and bullae. Photographs of the structures used to identify each species supplement the keys.