A Giant willow aphids (Tuberolachnus salignus) on a branch of Salix alba; larger aphids range from 5.1–5.7 mm B Bombus terrestris collecting honeydew from leaf litter beneath several branches bearing the aphids C holding a plastic plate beneath the aphid colonies to collect honeydew droplets D collecting honeydew droplets from the plate using a 5 μl glass capillary tube E compressing a worker bumble bee to force regurgitation of crop contents onto the plate F using a refractometer to measure solute concentration of honeydew.