Die Geschlechtsbestimmung beiMegaselia scalaris Loew (Phoridae)

Summary The determination of male sex of the Phorid,Megaselia scalaris, is effected through an epistatically-operating realizer which appears to lie terminally on a certain end of the chromosomes and which ist exchanged between the three non-homologous chromosomes by a regular translocation process. This process seems to be a praemeiotic event as the exceptional types often appear in clusters. Under the assumption that every cluster is the effect of one translocation, the translocation-frequency from the III-chromosome is estimated at ca. 0.3%, from the I-chromosome and from the II-chromosome at ca. 0.08%. The theoretical aspect of this type of sex determination is discussed. Details about the cytology ofMegaselia are reported.