Drosophila melanogaster

Drosophila melanogaster was originally a tropical and subtropical species. However, it has spread all over the world together with humans and hibernates in houses. The females are about 2.5 millimeters long, the males are slightly smaller. The latter are easily distinguished from the females by their more rounded abdomen, which is almost uniformly dark in colour due to melanins; the females have a more pointed abdomen when viewed from above, and have the black melanins incorporated more in the form of a transverse stripe pattern in the body cover (cuticle) of their posterior end. The eyes of the small flies are typically coloured red by the incorporation of brown ommochromes and red pterins.

The genus Drosophila in the classical sense comprises 1450 valid species and is the most speciose taxon of the Drosophilidae. Recent work based on phylogenomics (the study of relationships by comparing homologous DNA sequences), but also on morphology, for example of the male genital armature, has shown that the conventional genus Drosophila is paraphyletic. This means that some species, previously listed in at least eight but probably closer to fifteen other genera, are more closely related to certain species groups within Drosophila than they are to each other. The subgenus Sophophora Sturtevant, 1939 is relatively basal, that is, it splits off early from the remaining species complex (though it is itself also paraphyletic).

The normal procedure in such a case would be to split the major genus Drosophila and elevate the (Old World clade of the) subgenus Sophophora to generic rank, resulting in the recombination Sophophora melanogaster for our species. This would be more or less commonplace for fly taxonomists. However, it would have serious implications for applied research on the species, which is extremely important in this case, where even abbreviated Drosophila is often spoken of. To simply merge the nested genera into Drosophila as a supergenus would also have undesirable consequences: four different species would then be called Drosophila serrata and four others Drosophila carinata. Kim van der Linde tried to have Drosophila melanogaster retroactively declared the type species of the genus, which was rejected by the ICZN. Others suggested departing from the rules of cladistics and readmitting paraphyletic genera. The formal revision of the genus Drosophila has so far been omitted, and solely for this reason, so that Drosophila melanogaster continues to be the taxonomically valid name of the species, because so far no taxonomist has been willing to take responsibility for the consequences of the renaming.