Carpenter bees can display distinct colouration patterns due to structural coloured wings and/or coloured hairs on their bodies. Females of the sexually dichromaticXylocopa caeruleaare marked by strongly blue-pigmented hairs on the head, thorax and abdomen. The thorax of femaleX. confusais covered by yellow-pigmented hairs. The diffuse pigmentary colouration of the blue and yellow hairs is effectively enhanced by strongly scattering granules. The absorption spectrum of the blue pigment ofX. caeruleahas a maximum at 605 nm and is probably a bilin (a bile pigment). The absorption spectrum of the yellow pigment ofX. confusahas a maximum at 445 nm and may be a pterin. The thoracic hairs of femaleX. confusacontain also a minor amount of the bilin. The reflectance spectra of the pigmented hairs suggest that the pigments are tuned to the spectral sensitivity of the bees’ photoreceptors and provide spectral contrast with a green background.