Understanding the life cycle of native bees
June 3, 2015
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URBANA, Ill. - Most people know that the honeybee is the most economically important insect in the United States because of the pollination services it provides. However, some native bees such as leafcutter bees, carpenter bees, and digger bees don’t get the credit they deserve for contributions they make to our gardens and food crops, said University of Illinois Extension horticulture educator Kelly Allsup.

“Unlike non-native honeybees, the majority of native bees solitarily live in the ground or the pith of stems and are most likely not to sting because they do not need to defend the social colony,” Allsup said. “An understanding of the life cycle of some of these solitary bees will help in using their services in flower and vegetable gardens this spring.”

Most leafcutter bees are black or gray and smaller than an amber-colored honeybee. Allsup explained that these bees construct their nests in existing hollow cavities found in nature, or they may excavate a hole in rotten logs or twigs of plants such as roses.

The female constructs a series of cells using oval or semicircular pieces of leaf tissue to separate her chambers. “Damage is not usually noticed, but these leaf-cutting bees prefer foliage from rose, lilac, ash, sassafras, and Virginia creeper. She then leaves a mix of pollen and nectar paste as a provision for her growing larvae,” Allsup said.

The leafcutter bee, known as the mason bee or blue orchard bee, uses mud as its primary construction material. Many orchardists and gardeners can drill holes in wood or provide prefabricated mason bees nests consisting of long, hollow tubes. These bees will find existing cavities to construct their nests. The larvae will then overwinter and pupate in the spring.

“Those who culture (raise) these bees will bring the nests inside to ensure survival throughout the larval and pupal stage,” Allsup said. “Adults emerge for only a short period of time in the late spring and summer to collect pollen and rear young.”

Carpenter bees have a reputation as a nuisance insect because of their wood-boring activities on unpainted wood surfaces. The larger carpenter bees nest in solid wood and the smaller ones nest in hollowed-out stems of plants such as roses, sumac, and elderberry. Larger carpenter bees are usually yellow and black and can resemble, or be the same size, as a bumblebee, Allsup explained. Smaller carpenter bees are dark with a metallic sheen.

“Male bees do not sting but buzz at you to deter you away from the nest,” Allsup said. “The young adults will hibernate in nests over winter. Starting in spring, the newly mated females will either excavate a new tunnel or clean out old ones, dividing the cells with stockpiles of pollen and nectar, and lay eggs. These eggs will be adults in August and ready to overwinter.”

Digger bees are solitary bees that stock underground nests dug in the soil with pollen and nectar. They can appear to live in colonies because they are attracted to certain soil types, drainage and slope. The female lines her cells with an oily substance to keep it waterproof. The larvae winter and pupate in the spring and early summer, emerging for a short period. 

“To encourage these great pollinating bees to your flower and vegetable garden, limit or eliminate pesticide use, plant natives that have long bloom times, create habitats that may be out of the elements such as a wood pile, and provide many layers consisting of shrubs, perennials, groundcovers, and small flowering trees to your garden,” Allsup said.

Visit beespotter.org for more information on Illinois native bees or http://www.illinoiswildflowers.info for more information on Illinois native bloomers.