The effect of host-patch size and maternal crowding on the progeny sex ratio (PSR) of an aphid parasitoid Binodoxys indicus was examined. Increasing the number of hosts per individual female parasitoid (mother) colonising a host-patch always decreased the PSR, i.e., it favoured the yield of more daughters while increasing the number of mothers colonising a large host-patch always increased the PSR, i.e., it favoured the production of more sons. The extent of variations in the PSR at different levels of maternal crowding was compared with the prediction of the Hamiltonian LMC model, i.e., p=(n-1)/2n, where p=PSR and n=number of mothers colonising a host patch. The perception of trace odours of conspecific females and encounter with conspecific males induced haploid and diploid oviposition, respectively. The inversely parasitold-density-dependent PSR indicates that for obtaining maximum number of daughters in mass breeding, the initial ratio of host to female parasitoids should not be less than 100:1 at a time. none