Systematic alterations of the central amino acid in the peptidic juvenile hormone analogues consisting of three parts connected by amidic bonds tert.-butyloxycarbonyl group - amino acid - p-aminobenzoic acid ethylester) have revealed that the hormonal activity is dependent on the L-configuration of the central amino acids. The compounds exhibit specific activity on insects of the family Pyrrhocoridae, being inactive on several other insects tested.