The chromosomes of the weevil, Blosyrus japonicus Sharp, have been investigated in Hokkaido. A triploid parthenogenetic race (3x=33) was found in Ishiyama-rikkyo, Sapporo. The species is now known to have four parthenogenetic races, 3x, 4x, 5x, 6x, as well as a diploid bisexual race. All these races have been found in Japan. This represents the highest number of different polyploid races observed in any parthenogenetic weevil.
The Genetics Society of Japan