Diaminopropane, putrescine, norspermidine, spermidine, norspermine and spermine were commonly found in the larval silk gland and head of Bombyx mori, Antheraea yamamai and Galleria mellonella. The cockroach Periplaneta americana contained homospermidine, aminopropylhomospermidine and homospermine in addition to the common polyamines. This is the first report to show the occurrence of the homospermidine derivatives and a hexamine in insects. In addition to thermospermine, caldopentamine, and other usual polyamines, three cadaverine-derivatives, aminopropylcadaverine, bis(aminopropyl)cadaverine and aminopentylnorspermidine, were detected in the silk gland and head of Nephila clavata and Araneus ventricosus. The occurrence of aminopropyl derivatives of cadaverine and agmatine has never been reported in animals.