Monday, April 17, 2017

Pollinator of the Week: Halictid Bees by Donna Duffy

Sweat bee on wild rose,  photo courtesy LuRay Parker, Wyoming Wildlife

In honor of the upcoming National Pollinator Week (June 19-25), we are highlighting a different pollinator every week. This week's pollinator is the Halictid bee, commonly known as sweat bees.  Thanks to Vince Tepidino, USDA ARS, Bee Biology and Systematics Lab in Logan Utah for the following information.

Pollinators have distinct foraging characteristics – some are specialists that collect pollen from flowers of just a few kinds of plants. Others, like the Halictidae (sweat bees), seem to be "anti-specialists". To paraphrase the early 20th century humorist Will Rogers, they have never met a flower they did not like, and they rarely find one whose pollen or nectar is unyielding. Such generalists visit a wide variety of flowers and often seem to do so indiscriminately. Variety seems to be the spice of their foraging lives. 

Sweat bee on wild garlic, photo courtesy James H. Cane, Bee Biology & Systematics Lab,  Logan, Utah

There are problems for generalist foragers. One difficulty is metabolizing the contents of pollen grains of different plant species. While pollen grains contain most of the nutrients required by adult bees to mature and rear their offspring, plant species are by no means uniform in their pollen constituents. Indeed, pollen grains of some species contain toxic compounds. Thus, digesting pollen from many flower species, as generalists must do, may require more sophisticated metabolic and detoxification systems than possessed by bees that specialize.

Another problem for generalist foragers is learning how to manipulate flowers of many plant species, each unique in floral morphology. Several studies have shown that workers of social bees such as honeybees and bumblebees forage less efficiently the more flower types they visit. Social bees solve this problem by having individual workers specialize on different plant species, rather than generalize. The hive is thereby, generalized in its flower diet. 

In contrast, in halictids, even though many species display rudimentary social behavior, individual foragers are the generalists. Learning in halictid bees has not been studied, but their ability to forage indiscriminately may signal that they are the unrecognized geniuses of the bee world.