Dacus Fabricius, Syst. Antliatorum, 272, 1805. This genus has been divided into a number of genera or subgenera, according to the views of various workers on the family, and the species before me falls in the subgenus Bactroccra. The only character distinguishing the concept from Chactodacus is the presence of one or two oblique dark fasciae on the disk of the wing in addition to the one over the anal cell. In my paper dealing with this family [Insects of Samoa 6(7):253-266, 1931], I presented a key to the then known Pacific island species of this group, and in that key the Guam species runs clown to D. distinctus Malloch, but it is readily distinguished therefrom by the wing markings and other characters noted below.

Published as part of Mailoch, J. R., 1942, Trypetidae, Otitidae, Helomyzidae, And Clusiidae of Guam (Diptera), pp. 201-210 in Insects of Guam I, Honolulu, Hawaii :Bernice P. Bishop Museum on page 201, DOI: 10.5281/zenodo.5163626