(A) We inferred TART-A copy number for 151 DGRP strains using published Illumina sequencing data [80,81] and retrieved expression values for nxf2 from microarray data from whole adult females [125]. We found that TART-A copy number is significantly negatively correlated with nxf2 expression levels, as expected if TART-A piRNAs are targeting nxf2 for suppression (Spearman’s rho = −0.48, P = 4.6e-10). (B) We also compared piRNA production from TART-A and nxf2 across 16 DGRP individuals using data from [85]. There is a strong positive correlation between TART-A piRNA production and nxf2 piRNA production (Spearman’s rho = 0.89, P < 2.2e-16) across the 16 DGRP strains. (C) We also compared nxf2 expression to the amount of TART-derived piRNAs that align to nxf2 across these same strains. In this case, we observe a negative correlation, slightly larger in magnitude than what we see for our comparison of nxf2 expression and TART-A copy number (Spearman’s rho = −0.51, P = 0.046). Underlying data can be found in S2 Data. DGRP, Drosophila Genetic Reference Panel; piRNA, Piwi-interacting small RNA; RPM, reads per million.