Cuticular lipids of female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae)

The cuticular lipids of the cavity-nesting adult female solitary bees, Osmia lignaria Say and Megachile rotundata (F.) (Hymenoptera: Megachilidae), were analyzed by gas chromatography (GC) and combined GC–mass spectrometry. The cuticular lipids of these female bees are mainly consisted of hydrocarbons. For O. lignaria, nearly 64% of the cuticular lipids were C25–C31 mono-alkenes. For M. rotundata, 48% of the cuticular lipids were C23–C33 alkanes with nearly the same quantities of the same chain-length mono-alkenes (45%). For the mono-alkenes of O. lignaria, 14 mono-alkene constituents were identified, with two of these, 9-heptacosene and 7-nonacosene, comprising 67% of the total alkene distribution. For M. rotundata females, the mixtures of mono-alkenes were more complex with 26 constituents identified and quantified. For the M. rotundata mono-alkenes, 57% of the total composition consisted of the three alkenes, 7-pentacosene, 9-pentacosene and 7-heptacosene. For both bee species, small quantities of C40–C48 wax esters were also characterized with the major components possessing a C18 mono-unsaturated fatty acid (9-octadecenoate) moiety esterified to even-carbon number (C22–30) fatty alcohols. The possible role of these cuticular lipids as nest recognition chemicals is discussed in light of nesting behavior of managed crop pollinators.