The mutant "proboscipedia" in Drosophila melanogaster - A case of hereditary homoösis

The recessive mutant "proboscipedia", found byBRIDGES April 27, 1931, has its locus in the third chromosome at approximately 5.3 units to the right of Dichaete, or at 45.7.In proboscipedia the oral lobes are converted into a labium-like organ, which also resembles a pair of antenna-like or tarsus-like appendages. This change, as well as the modifications of the labrum, maxillae, maxillary palpi, and other structures give to the mouth parts of proboscipedia a resemblance to those of the biting type found in insects of lower orders.The four-fold resemblance of the modified oral lobes in proboscipedia to the labrum, the maxillary palpi, the antenae and the tarsi is comprehensible in view of the homology of these three head-appendages with each other and with the walking legs.