Brood sex ratio determination by flow cytometry in ants

Sex ratio variations during brood development have important implications for the study of sex allocation in haplodiploid insects. So far, few studies have addressed this question because of the difficulty to determine the sex of the brood. We used flow cytometry to differentiate haploid males from diploid females in the ant Linepithema humile. Our data show that flow cytometry can be used successfully to distinguish between male and female brood on the basis of their DNA content, from the very first larval stage. Moreover, we show that flow cytometry allows sex brood determination in other ant species, as well as in nonsocial Hymenoptera.