Abstract
1) Salivary gland chromosomes of Drosophila nigromaculata obtained from natural populations in Hokkaido has revealed a remarkable chromosomal polymorphism. Twenty-two different inversions were found in heterozygous condition in 57 samples, in total 101 inversions being recorded; 26.3 in percentage. The inversions were found in the X, A, B, C, and D arms, while the dot-like E arm showed no aberration in samples so far studied.
2) The frequency of inversions in each chromosome was as follows; 9.11% for C, 6.77% for D, 6.51% for A, 2.34% for B and 1.56% for X.
3) A possible meaning in adaptation of non-random association of inversions was suggested.
