DIPLOGASTER (DIPLOGASTRELLUS) CEREA SP-N FROM SAGUARO CACTUS ROT AND A REVISION OF THE SUBGENUS DIPLOGASTRELLUS (NEMATODA, DIPLOGASTRIDAE)

A new species of Diplogaster is described from decaying cactus in Ariz ona, USA. It is characterized by a single female gonad, a quite short postvulvar uterine sac with paired pouches, and a keel shaped gubernac ulum, proximally notched, with an interrupted caudal margin. Its dauer larvae are phoretic on beetles and Diptera from the same habitat. Char acters of the ground pattern of Diplogaster sensu Into are reconstruct ed to discern apomorphies for the subgenus Diplogastrellus of Diplogas ter. Within this subgenus three transformation series of the pattern o f male caudal papillae are recognized. We comment on the phylogenetic relationships of the twelve species in this subgenus and provide male and female keys to species, as well as information on their habitats a nd geographic distribution. Our reexamination of type material reveale d that Diplogaster microstoma Goodey, 1929 is conspecific with D, grac iloides Skwarra, 1921. The new name Diplogaster heynsi nom. nov. is pr oposed for Metadiplogaster secundus Dassonville & Heyns, 1984. Diploga ster minor Cobb, 1893 is synonymous with D. parva Cobb, 1893. Acrostic hus toledoi Rahm, 1928 is placed in the Nudicapitatus-group of Diploga ster. Diplogaster attenuatus Cobb in Banks & Synder, 1920 is a nomen n udum.