AbstractWhole body extracts of the two‐spotted spider mite (Tetranychus urticae Koch) were analyzed using a 16‐channel electrochemical array high performance liquid chromatography (HPLC)‐based detection system that allows the simultaneous isolation and identification of a variety of biogenic amines. The spider mite extracts were found to contain the biogenic amines octopamine, dopamine, and 5‐hydroxytryptamine (5‐HT), as well as several precursors and metabolites including tyrosine, tyramine, tryptophan, and N‐acetyl octopamine. Differences in the levels of biogenic amines were observed between eggs and the adult stages and between males and females. This is the first direct determination of biogenic amines in the Tetranychidae and the first demonstration of 5‐HT in any mite species. © 1994 Wiley‐Liss, Inc.