A new neuropeptide hormone was isolated from the corpora cardiaca of the periodical cicadas, Magicicada species. Primary structure of the peptide as determined by a combination of automated Edman degradation after enzymatic deblocking with pyroglutamate aminopeptidase and mass spectrometry is: pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn-NH2. Synthetic peptide assayed in the green stink bug Nezara viridula caused a 112% increase in hemolymph lipids at a dose of 0.625 pmol, and a 67% increase in hemolymph carbohydrates at a dose of 2.5 pmol. Based on these results we designate this peptide, a first from order Homoptera, as Magicicada species-adipokinetic hormone (Mcsp-AKH).