Abstract.Using heterologous and conspecific bioassays, two peptides have been isolated from methanolic extracts of corpora cardiaca from the pyrgomorphid grasshopperPhymateus morbillosusL.The structures of both peptides were elucidated by a combination of Edman degradation, after deblocking the N‐terminal pyroglutamic acid residue, and mass spectrometric techniques.One peptide is an octapeptide (pGlu‐Leu‐Asn‐Phe‐Ser‐Thr‐Gly‐TrpNH2) which also occurs in other insects and is code‐named Scg‐AKH‐II.The second peptide is a novel decapeptide member of the AKH/RPCH family (pGlu‐Leu‐Asn‐Phe‐Thr‐Pro‐Asn‐Trp‐Gly‐SerNH2code‐named here Phm‐AKH.It is the first example of a different peptide in the same genus.The analysis of changes of metabolites in the haemolymph, fat body and flight muscles of maleP.morbillosusduring a 30 min flight and rest after flight reveal an overall picture of flight metabolism similar to that ofLocusta migratoria.Carbohydrate‐fuelled metabolism is pronounced during the first 15 min of flight, whereas lipid‐based metabolism is mainly used thereafter.By analogy with work onL.migratoria, it is concluded that the endogenous peptides