Sitophilus sasakii (Tak.) (Coleoptera: Curculionidae) in Canada: Anatomy and Mycetomal Symbiotes as Valid Taxonomic Characters

Abstract

Large and small strains of the rice weevil Sitophilus oryza (L.) (Calandra oryzae (L.) of authors following European usage) have been reported from several localities (Birch, 1944 in Australia; Kiritani, 1956 in Japan; Kono, 1955 in Nepal; Richards 1944 in Britain; and Utida, 1958, in Canada, Japan and U.S.A.). Birch and Richards both seem to have considered it probable that the two strains were separate species: but they did not make the separation. Floyd and Newsom (1960), after careful work on both strains found in the U.S. and reared in the laboratory on a variety of materials, decided that the small strain could be validly made a separate species, thus agreeing with Takahashi who, according to Floyd and Newsom (1960), had elevated this strain to species rank as Calandra sasakii. In conformity with modern North American usage Floyd and Newsom refer to this small species as Sitophilus sasakii (Tak.). In addition to differences in size, they found differences in the male and female genitalia, interstrain sterility and various ecological differences. There were also differences in pronotal markings as had been, according to Kono (1953), noted by Takahashi (1928). Kono states “…the adult of the large strain has pits dotted densely on the central part of the pronotum, the small strain does not, and, furthermore the shape and size of the pits differ distinctly”.