Drosophila reproductive behaviors are directed by fruitless neurons (fru P1 isoforms). A reanalysis of genomic studies shows that genes encoding dpr and DIP Immunoglobulin superfamily (IgSF) members are expressed in fru P1 neurons. Each fru P1and dpr/DIP (fru P1 ∩ dpr/DIP) overlapping expression pattern is similar in both sexes, with dimorphism in neuronal morphology and cell number. Behavioral studies of fru P1 ∩ dpr/DIP perturbation genotypes point to the mushroom body functioning together with the lateral protocerebral complex. Functionally, we find that perturbations of sex hierarchy genes and DIP-ε changes sex-specific morphology of fru P1 ∩ DIP-α neurons. A single-cell RNA-seq analysis shows that the DIPs have high expression in a restricted set of fru P1 neurons, whereas the dprs are expressed in larger set of neurons at intermediate levels, with a myriad of combinations
