Abstract
In a grasshopper, Acrida lata, some male specimens have been found to contain 1, 2, or 3 B chromosomes in addition to the normal complement 2n_??_=22+X, while others to contain none. The frequencies of the specimens with B's varied locally from 7 to 31 per cent according to the populations sampled, in 1959, from 9 localities in the northern part of Kyushu, Japan. In a population, which studied in succeeding 3 years from 1957 to 1959, the frequency of animals with B's slightly fluctuated from year to year, i. e., 32, 34, and 30 per cent in frequency. The B's of different populations were the same in cytological feature and behavior, suggesting their common origin in the remote past of the species. This in turn would explain why the same B's are distributed wide in natural populations. Mechanism of the population dynamics remains for further investigations.
