Three RFamide-immunoreactive peptides were isolated from headless Aedes aegypti mosquitoes. Their structures were identified by Edman degradation or a combination of amino acid composition analysis and mass spectrometry to be: Aedes head peptide 1 [23], [Pro4]-Aedes head peptide (i.e., pGlu-Arg-Pro-Pro-Ser-Leu-Lys-Thr- Arg-Phe-amide), and Leu-Lys-Thr-Arg-Phe-amide which have been named Aedes head peptides 3 and 4, respectively.