(a) Visual markers present in homozygous FL lines (GFP, left) and EGI lines (red eyes, center) are present in SSIMS flies generated via the mating scheme in Appendix 1—figure 1. (b) Counts of male (pink) and female (blue) offspring of SSIMS strain raised in food with 10 μg/ml Tetracyline (Tet) and without Tet. No females offspring were observed when larvae are raised in the absence of Tet. Chi-squared test shows significant difference from expected 50:50 ratio of males:female, n = 10 per group, *** denotes < 0.0001. (c) Counts of egg-lay (light gray) and surviving adults (dark gray) of wild-type females crossed with either wild-type or SSIMS males. SSIMS male mate successfully with wild-type females, producing slightly more eggs, but no adult offspring emerge, n = 5 per group, *** denotes p < 0.0001. (d) Percent female offspring when SSIMS stocks are reared in food with increasing concentrations of Tet, n = 10 per group. (e) Percent female offspring when respective progeny from (d) are reared in food without Tet, n = 7–10 per group. Line behind data shows Hill function that fits data with statistics described in the main text. (f) Percent female offspring when progeny from the 100 μg/ml group in (e) are reared in food without Tet, n = 30. FL, X-linked Female Lethal; EGI , engineered genetic incompatibility targeting pyramus; WT, wild-type; SSIMS, sex-sorting incompatible male system; Tet, Tetracycline.