CHEMOTAXONOMY OF WATER BEETLES BASED ON THEIR PYGIDIAL GLAND CONSTITUENTS

The mainly aromatic pygidial gland constituents of 45 water beetle species (Hydradephaga; Dytiscidae, Haliplidae) have been investigated. Chemical data were obtained by mass spectrometry, thin layer and gas chromatography and UV-spectrometry. Investigations on Agabus melanarius showed these gland substances were species specific and constant. Seasonal quantitative variations are probably due to variations in population structure and overwintering bionomics. The phylogenetic tree based on the distribution of pygidial gland constituents shows that taxa fall into three chemical groups (sesquiterpenes, aromatic compounds, hydroxycarboxylic acids). This grouping is generally in accordance with other taxonomic conceptions. Other chemical differences correspond to the morphology of the larva and pupa (Copelatus, Hydroporus melanarius). The position of several chemically diverging taxa (Haliplidae, Laccophilinae, Hydaticus) should be clarified by using further techniques such as morphology or considering the biogenesis of the water beetle compounds. © 1979.