oa African Entomology - Xylose as a nectar sugar: the response of Cape honeybees, Apis mellifera capensis Eschscholtz (Hymenoptera: Apidae)
The pentose sugar xylose has recently been reported as a major sugar in the nectar of Protea and Faurea (Proteaceae). Because honeybees are potentially important pollinators of both Protea and Faurea, we investigated the responses of Cape honeybees to xylose solutions. Preference tests were conducted outdoors using a single colony of bees trained to visit feeding dishes. Sugar solutions (20 or 40 ml, usually 30 % w/w) were set out at 13:00, and the number of bees on each dish was recorded at IS-min intervals. The tests showed: (1) that pure xylose is unattractive compared to the common nectar sugars; (2) that bees presented with a range of glucose/xylose mixtures prefer those with the smallest proportion of xylose; (3) that xylose has a repellent effect, the bees preferring, for example, 9 % glucose to 9 %glucose + 21 % xylose. During survival tests, 50 or 100 newly-emerged bees were placed in Liebeveld cages, each with a wax comb and two gravity feeders. Cages were kept at 30 C, and dead bees were removed and counted daily. When bees were fed sucrose, glucose, fructose and xylose (all 30 % w/w) and water only, survival on xylose was as poor as on water. With different glucose/xylose mixtures, survival time was inversely related to the proportion of xylose in the diet, each 5 % increment in xylose causing an additional increase in mortality. We conclude that the xylose in Protea and Faurea nectar is not there for the benefit of honeybees.
Article metrics loading...