A new nematode, Anomalomermis ephemerophagis n. g., n. sp. (Nematoda: Mermithidae) is described from the mayfly Ephemerella maculata Traver, 1934 (Ephermeroptera: Ephermerellidae) in California. The new species is characterized by 6 cephalic papillae and 4 additional disk papillae located on the head between the cephalic papillae and stoma. Additional diagnostic...