Cytological evidence of male heterogamety in sex determination of Telmatoscopus albipunctatus (Diptera: Psychodidae).

Telmatoscopus albipunctatus is polymorphic for several polytene chromosome bands. In examining the inheritance of a polymorphic heterochromatin-like band in chromosome IV we verified that it is inherited like a sex-linked factor. There are two types of chromosome IV in regard to this band: one bears a very thick heterochromatin-like band (H+), and the other bears a thinner corresponding band (H-). Three kinds of combinations are found in our stocks: H+H+, H+H- and H-H-. All three combinations can be found in females; however, in males, only the combinations H+H- and H-H- are found. Through specific crosses, it was concluded that the sex determining factor is located in chromosome IV in close vicinity to these bands.