The metaphase configurations of 400 strains from 63 species of Hawaiian Drosophila were determined from squash preparations of larval brain tissue or spermatogenic cells from adult testes. These karyotypes include configurations from seven species not previously described. Metaphases of 148 Hawaiian species have been recorded, including species of the "picture-wing" group, the "modified mouthpart" group, and the "bristle-foot" group. A comparison between Hawaiian species and non-endemic species was made on the basis of chromosome numbers and configurations. Among the Hawaiian species, 85.8% have retained the primitive haploid configuration of five rods and one dot compared with only 34.8% of species from the rest of the world. In only 4.7% of Hawaiian species is the chromosome number reduced from the basic haploid number of six, whereas it is reduced in 47.6% of the species from other areas. Most of the changes in chromosome size and shape among the Hawaiian species seem to be the result of added heterochromatin or chromosome fusions; no evidence of pericentric inversions has been found in modified karyotypes.

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