Nutritive value of 15 single pollens and pollen mixes tested on larvae produced by bumblebee workers (Bombus terrestris, Hymenoptera: Apidae)

Laboratory trials were performed at 27 °C on micro-colonies comprised of three Bombus terrestris workers. They were fed with syrup and pollen paste ad libitum. The micro-colonies were terminated on the 14th day after egg-laying. Two bioassays tested the nutritive value of 6 pure pollens and 9 commercial pollen mixes on bumblebee larvae. Among 10 criteria tested, the most sensitive to the different pollens were the mean weight of larvae and the rate of discarded larvae. Differentiation between treatments was easier with single pollens that ranged from 14.4% to 24.9% crude protein for Helianthus and Castanea respectively, than with mixes that ranged from 12.9% to 17.6%. The best performance ranking was assigned to Castanea, Papaver and Rubus , which produced larvae weighing 110–150 mg, the lowest to Helianthus and Cistus which resulted in larvae of 20–50 mg. The largest larvae (240 mg) were produced with the mix at 96% Brassica and 15.9% protein and the smallest with the mix at the lowest protein content (12.9%) assembling Picris, Hedera, Amaranthus, Solanum, Helianthus and graminaceae .