Sex-specific expression of the Dsx-GFP transgene. A mix of wild-type and heterozygous DSX first instar larvae observed under a fluorescence microscope with a 5x objective. Red fluorescence (upper panel, left) denotes larvae carrying the DsRed transgene (the upper larva shows its dorsal side, the four additional red larvae show their ventral side). Green fluorescence intensity (upper panel, right) allows distinguishing between females (less bright, arrowheads) and males (showing stronger fluorescence). Lower panels: left, transmission image; right; overlay of images on upper panels.