NATIVE BEES

photo by Judy Gallagher

Native Bees

Tiger Swallowtails Puddling - Photo by Judy Gallagher

According to recent estimates, there are 456 native bee species in Virginia. They are in six families whose common names often reflect their nesting habits: Carpenter bees build their nests in bare wood, mining bees (or Andrenids) dig nests in bare ground, leafcutter bees cut small holes out of leaves to line nesting cells for immature bees, and mason bees cap their nest cells with mud. Sweat bees are so named because they are attracted to people’s sweat, for the salt, and bumble bees bumble and buzz as they forage on flowers.

Most native bees are solitary rather than social and do not nest in colonies. With no colony to defend, solitary bees, as a rule, do not sting. Bumble bees are the only truly social native bees in the U.S. (honey bees are also social but are not native). Native bees range in size from less than 1/8” to over 1” long. They vary greatly in color from brown or black to metallic green or blue and may have stripes of red, white or yellow. Many look like small flies.

Native bees play a vital role in pollinating native plants and trees as well as food crops. Bumble bees are particularly important pollinators because they buzz pollinate by vibrating their flight muscles while clasping a flower, dislodging pollen that is difficult to access. This ability makes bumble bees more effective pollinators of many plants than other bees, such as honeybees, that cannot buzz pollinate. Bumble bees are highly efficient pollinators for food crops as well as native plants and are vital to tomatoes (one of the only insects that can pollinate them), cranberries, blueberries, plums, apples, peppers, and alfalfa.

The life cycle of bees resembles that of butterflies, in that they metamorphose from egg to larva to pupa to adult. Individual bees may live a year or longer, but only a few weeks are spent as adults. Most of a bee’s life is spent in a nest cell provisioned by its mother with a loaf of pollen to nourish the developing bee.

Many bee species are generalists and gather pollen from any flower source. Others are specialists who are very particular about the pollen they collect for their offspring. There are 123 specialist bee species in Virginia that gather pollen only from certain native plant species. The mutual relationship between specialist bees and their special plants evolved over millennia, and both bees and plants suffer without the other.

Spicebush Swallowtail - Brown - Judy Gallagher

  
    What Native Bees Need
    How Can We Help
 
    Food and Water: Bees' nutritional needs are almost entirely met by flowers. Adult bees eat a little pollen and a lot of nectar, and they feed their larvae a lot of pollen, often mixed with a little nectar. 
Different bees have evolved to gather nectar from flowers with different shapes.  Some bee species have long tongues that enable them to suck up nectar from flowers with long, tubular necks, such as beardtongues.  Others have very short tongues they use to sop up nectar from shallow, flat flowers like those in the sunflower family. 
Bees have good color vision and are particularly attracted to blue, purple, white or yellow flowers. They cannot see red very well, which is why red-flowered plants usually depend on pollinators other than bees (e.g. Cardinal lobelia is pollinated by hummingbirds, while its cousin Blue lobelia is pollinated by bees).
Specialist bees only gather pollen from certain native plant species.
Native plants required by bee specialists are threatened by invasive plants.  For example, the native Spring beauty (Claytonia virginica) is being displaced from moist woodlands by the invasive Lesser celandine (Ficaria verna), threatening the Andrena erigeniae bee that depends on Spring beauty.

       Plant flowering native plants.  Include plants with a range of bloom times, from early spring to fall, to support bees over the growing season. Plant a diversity of flowering native plants with varying flower shapes to support a diversity of bee species.
 Plant flowers in clusters to maximize visibility.
Plants that support specialist bees will also support generalist bees. Flowers in the Goldenrod (Solidago), Aster (Symphyotrichum), and Sunflower (Helianthus) genera are most likely to support specialist bees. Trees and shrubs that support specialist bees include Willows (Salix), Redbud (Cercis canadensis), Silky dogwood (Cornus amomum), and Winterberry (Ilex verticillata). Some weedy natives, such as Violets (Viola) and Frost asters (Symphyotrichum pilosum), support specialist bees and are excellent pollinator plants, so don't pull them up!
Remove invasives that threaten to displace the native plants that specialist bees require.

    Breeding and nesting:  Solitary bees may nest together if a good site is found, but construction, food gathering, and egg-laying are individual. Most species dig a tunnel in bare or partially vegetated soil. Some use abandoned beetle burrows or rodent burrows. Others nest in tree and plant cavities, including hollow stems. A few species construct nests out of mud, plant resins or saps, along with tiny particles from rocks or trees. Mason bees and leafcutter bees use soil or leaf material to separate individual larval cells. Some nests have only a single brood cell, but most have 10-50 or more.

     Provide waxy-leaved plants such as Redbud and Virginia creeper for leafcutter bees. A patch of wet, bare soil during the early spring nesting period, or even a bucket of mud can help mason bees construct their mud casings. 
      
Provide nesting habitat for a variety of species: Leave the dried stems of perennial plants standing through the winter for twig-nesting bees to burrow into and build nests. Leave (or add) logs and woody debris. Leave undisturbed areas of bare ground for ground-nesting bees.

   Reduce hazards:  Bees are threatened by habitat loss and by use of pesticides. Broadcast spraying for mosquitoes kills bees and other insects. Diseases and parasites may spill over from commercial agricultural and managed bee operations into wild bee populations.  One bee species (the Rusty patched bumblebee, Bombus affinis, found in Fauquier and four western Virginia counties) is the only insect federally listed as an endangered species. 

     Do not use insecticides in your yard.  It will kill the bees, and contaminate the pollen and nesting materials they gather for their young. Never broadcast spray for mosquitoes in your yard.
Do not buy plants that have been treated with insecticides, or grown from seed that was treated with neonicotinoids.

Resources:

To identify flowering native plants that will provide nectar and pollen throughout the bloom period, consult Plant Nova Natives' bloom timetable and their more comprehensive Plantfinder which includes bloom times for native flowering plants in Northern Virginia.

To learn more about the native plants required by specialist bees, see Virginia Native Plant Society's summary of a presentation by Sam Droege and their list of plants for specialist bees.

To identify specialist bees and their plants, see Pollen Specialist Bees of the Eastern United States, by Jarrod Fowler and Sam Droege, 2020.

Where to see Swallowtails and their habitat:

Huntley Meadows Park, Occoquan Bay National Wildlife Refuge, Manassas Battlefield Park, and Meadowlark Gardens Regional Park.