The cuticular lipids from two megachilid bees, the alfalfa leafcutting bee, Megachile rotundata (F.) and the blue orchard bee, Osmia lignaria Say, were identified and percentage compositions were determined for the various lipid classes. Lipids were sequentially extracted from both adult male and female bees with hexane and chloroform. Lipid components were separated and quantified using gas chromatography-flame ionization detection (GC-FID). Structural identifications of cuticular lipids and their derivatives were determined using GC-mass spectrometry. Major cuticular lipids for both species were identified as homologous series of hydrocarbons and lesser amounts of wax esters. The hydrocarbon fractions consisted of chain length mixtures of n-alkanes and monounsaturated alkenes. Positional isomers of monounsaturated alkenes were identified by GC-MS of their dimethyl disulfide derivatives. The major wax ester chain lengths were C40-C46 and the acid moieties were mainly monounsaturated fatty acids. The roles of the cuticular lipid in regard to desiccation avoidance and nesting site recognition are discussed.