Cuticular and Dufour’s gland chemistry of two solitary cavity-nesting bees

The contents of the Dufour’s gland of the solitary bees Megachile rotundata and Osmia lignaria are suspected to be the source of individual nest recognition cues applied to the inner walls of nest cavities.  Furthermore, in bumble bees, the chemistry of the Dufour’s gland has been shown to match that of the cuticle.  Field- and lab-reared female bees were freezer-killed.  For each bee, we solvent-extracted first the cuticular components and next the Dufour’s gland contents for analysis with gas chromatography coupled with flame ionization detection and also with mass spectrometry.  Therefore, we obtained the chemical profile (percent composition) of each individual bees’ cuticle and Dufour’s gland.  Using principal components analyses for each species, we searched for factors that discriminate between the chemical compositions of 1) field and lab-reared bees and of 2) cuticles and glands.  We also explored the level of unique matching of an individual bee cuticle with her Dufour’s gland.