According to a further aspect, the present invention provides a double stranded RNA molecule that down regulates expression of an insulin-like factor gene of the androgenic gland of M. rosenbergii (Mr-IAG) comprising a sense strand and an anti sense strand, the sense strand and the anti sense strand together form a duplex, said anti sense strand comprises a nucleotide sequence that is at least 70% complementary to the nucleotide sequence set forth in SEQ ID NO:1 or a homolog or fragment thereof.