The Drosphila melanogaster species-group, established by Sturtevant (1942) for fourteen species, is now known t o contain 115 described species here divided into twelve named subgroups (including one newly proposed), as well as further undescribed species. Three of the species, melanogaster, simulans and ananassae, are cosmopolitan; two others, kikkawai and malerkotliana, are widespread in the southern hemisphere, the latter apparently a recent introduction t o South America. The greatest numbers of species otherwise occur in the Oriental region with smaller numbers in the Ethiopian, eastern Palaearctic and Australian regions and in several islands of the South Pacific. Dmjasekari and D,raychaudhurii are synonymized with D. biamipes; Definition of the melanogaster species-group (Sturtevant, 1942: 29) As members of the subgenus Sophophora, species of the melanogaster group are characterized inter aliu by relatively narrow cheeks and possession (in most species) on the abdominal tergites of dark posterior bands 0307-6970/80/1000-0341 $02.00 0 1980 Blackwell Scientific Publications 24 34 1 342 Ian R . Bock 38,291-307. Zetterstedt, J.W. ( I 847) Diptera scandinaviae disposita et descripta, 6.

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Twenty autosomal inversions were detected in the polytene chromosomes of larvae obtained by hybridizing inversion-free strains of the species of the bipectinata complex (D. bipectinata, D. parabipectinata, D. malerkotliana and D. psewloananassae). Twenty autosomal inversions are also known as extant polymorphisms in these species; fifteen (possibly sixteen) of these inversions are different from those detected in the interspecific hybrids. The available evidence permits reconstruction of chromosome phylogenies deriving malerkotliana, pseudoananassae and a population ancestral to both bipectinata and parabipectinata directly from a common ancestral population. The results of the study support the Carson hypothesis of transitional homoselection during the processes of speciation.

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