Abstract The cuticular hydrocarbons of the Colorado beetle Leptinotarsa decemlineata say consist of 2-methylalkanes, internally branched monomethylalkanes, dimethyl-, trimethyl-and tetramethyl-alkanes. The hydrocarbons differ from those of most of the other insects so far investigated. The major components were found to be the dim ethyl branched alkanes, 2,6-and/or 7,22-dimethyl-octacosane and the tetram ethylalkane, 3,10,16,23-tetram ethyltritriacontane. The hydrocarbons identified are members of homologous series which differ by two m ethylene groups. The identification of hydrocarbons was achieved by mass spectrom etry and gas chromatographic determination of Kovats retention indices on two high efficiency capillary columns coated with Dexsil 300 and OV-1.