Bees without flowers: Before peak bloom, diverse native bees find insect-produced honeydew sugars

Authors: MEINERS, JOAN - University Of Florida; Griswold, Terry; MORGAN, ERNEST - University Of Florida

Submitted to: The American Naturalist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2017
Publication Date: 5/30/2017
Citation: Meiners, J., Griswold, T.L., Morgan, E.S. 2017. Bees without flowers: Before peak bloom, diverse native bees find insect-produced honeydew sugars. The American Naturalist. 190(2):281-291. http://dx.doi.org/10.1086/692437.
DOI: https://doi.org/10.1086/692437

Interpretive Summary: Scientists and amateur naturalists alike have long studied the complex relationship between bees and flowers. We know that different species of bees prefer certain colors or shapes of flowers, and that honeybees have devised an elaborate waggle dance communication system in order to direct other workers to the best floral resources. Recent reports have even detailed the extrasensory ability of some bees to detect floral nectar using humidity, or magnetic or electric fields. The ability of bees to find food that is not in flowers, however, is little known. Yet it may become increasingly relevant as global threats like habitat urbanization and climate change cause increasingly unpredictable blooming times. Here, we report and evaluate the first-known observation of a diverse community of native bees detecting and using of non-flower, insect-produced honeydew sugars in the absence of any standard cues bees use to detect flowers. Working in Pinnacles National Park, in the South Coast Range of California we recorded forty-four species of bees displaying non-floral feeding behaviors during the early bloom season. Not only does this finding imply that bees are using previously unknown complex and interconnected foraging strategies, but it may be evidence that wild, native bees can adapt and survive periods when there is a shortage of nectar.

Technical Abstract: Bee foragers respond to complex visual, olfactory, and extrasensory cues to optimize searches for floral rewards. Their abilities to detect and distinguish floral colors, shapes, volatiles, and ultraviolet signals, and even gauge nectar availability from changes in floral humidity or electric fields are well studied. Bee foraging behaviors in the absence of floral cues, however, are rarely considered. We observed forty-four species of wild bees visiting inconspicuous, non-flowering shrubs during early spring in a protected, Mediterranean habitat. We determined experimentally that these bees were accessing sugary honeydew secretions from scale insects without the aid of standard cues. While honeydew use is known among some social Hymenoptera, its use across a diverse community of solitary bees is a novel observation. The widespread ability of native bees to locate and use unadvertised, non-floral sugars suggests unappreciated sensory mechanisms, complex interspecific foraging dynamics, and potential critical resilience of diverse bees to environmental change.