The study of chromosomes in insects is a good tool in mitotic process analysis, zoographic localization and evolution investigation. Among them, the Sciaridae offers a karyotype with a small number of chromosomes, where the heterochromatin and nucleolar organizer region, NOR, are easily analyzed in metaphase chromosomes obtained from cerebral ganglia squashes. In this work, the heterochromatic regions on Bradysia hygida mitotic chromosomes, revealed by C-banding, were identified as centromeric blocks on A and C chromosomes and as dark interstitial region in B and X chromosomes. By Ag-DAPI staining, active nucleolus organizer region, NOR, was revealed associated to the constitutive heterochromatin in the end of the C autosome chromosome. The C-band regions and the unusual ribosomal site localization are discussed.