The Bees Beneath Our Feet
Do you ever wonder where that bumble bee goes once they have collected pollen from a flower? Or maybe you have questioned where that yellow jacket went after harassing you at your picnic?
Chances are that they’re going to the ground — as much as 70 percent of native bee species in the United States are considered ground nesters, meaning they make their nests under the ground or directly above it. Washington State alone has approximately 420 species of ground nesting bees living amongst us.
Ground nesting bees are mostly solitary bees that create underground nests; with the queen (or female) living individually and raising their own young. These solitary bees do not form hives, but several females may nest in the same area. Usually, the female bees are not aggressive and are unlikely to sting but may do so to defend their nest. The male bees may seem aggressive when they are seeking a mate, however they lack a stinger and are also harmless. Like other bee species, ground-nesting bees are active foragers of nectar and pollen, making them beneficial pollinators.
Ground nesting bees become active in early spring, and spend their time collecting nectar and pollen from flowers. Female ground nesting bees place a ball of nectar and pollen in a cell in their nest and lay an egg on it. The eggs hatch a few days later and the larvae eat the pollen and nectar for food. In the autumn, the adult larvae stay in their mothers’ underground nest and hibernate for the winter. By spring the following year, the adult bee leaves the nest to start collecting pollen and build a nest to continue the life cycle.
Adult ground nesting bees eat pollen and nectar from flowers, harvesting within a couple of hundred yards from their nests. They collect only as much food as they need to sustain themselves and their larvae. Ground nesting bees do not make honey — only honey bees make honey. They store only a little pollen and nectar in their underground nests to feed themselves and their larvae in the summer. The new bees hibernate in the cold months, so they do not need a food source for the winter. (In comparison, honey bees (Apis spp.) must turn nectar into honey to feed thousands of bees over the winter)
Nests: Ground nesting bees don’t build hives, they live in underground tunnels or above the ground in plant material, old stumps or abandoned burrows.
Bees that build underground nests prefer to build in dry soil. The solitary queen bee excavates nesting tubes or cells to lay her eggs in. The entrances to the nests are small piles or patches of bare soil. The nests are abandoned after the spring nesting season and eventually the soil washes back into place with rain, disappearing completely.
The bees that build aboveground nests are social bees, unlike the solitary underground nesting bee. They can construct their nests in fallen plant matter or small holes, often in old mammal burrows. An example of an aboveground nesting bee is a bumble bee.
Symbiosis with People
Ground nesting bees are very beneficial to our ecosystem and humans; and play a vital role in pollinating plants and food crops. To support ground nesting bees in a yard, the first step is to clear vegetation from a sunny, well-drained area. Don’t turn the soil in that area, as the bees need stable soil to nest in. The closer the nest site is to pollen and nectar sources the better so that the female bee can put their energy towards the offspring. An important step is to protect them from pesticides; ground nesting bees are very susceptible to exposures of contaminated soil. If you are bothered by ground nesting bees in your yard, try keeping the area damp or sprinkling water in their nest – the bees will relocate on their own.
This article from xerces.org has more information on how to support ground nesting bees in your habitat.
For a more in-depth look at bees watch DNDA’s Wetland Workshop: What’s the Buzz on PNW Pollinators?!
The Common Acre has a handy weatherproof pocket guide to learn how to identify Bees of the Puget Sound Lowlands from Bellingham to Olympia.
Sweat Bee or Alkali Bee (Halictidae): The sweat bee or alkali bee is a small ground nesting bee. They got their name because some species collect salt from mammal sweat. They are small and inconspicuous, usually black or metallic grey, but can be vibrant and pearly opalescent in color. These bees dig tunnels in soft soil and form a nest chamber. There are at least 60 species in the Pacific Northwest.
Mining Bee or Burrowing Bee (Andrenidae): The mining bee or burrowing bee can dig tunnels up to 10 feet long. They prefer to nest in an undisturbed dry spot with little vegetation. This solitary bee often has a fuzzy orange or yellow thorax and a dark abdomen with light stripes. There are approximately 200 species in Washington.
Yellow-faced Bee or Plaster Bee (Colletidae): The yellow-faced bee or plaster bee uses sticky nectar to glue soil together to form the walls of their egg chambers. Some of these bees are small and others are robust. Instead of carrying pollen on its body hair (like most bees) they carry pollen mixed with nectar in their crops and will regurgitate it for larvae in the nest. There are at least 30 species in the Pacific Northwest.
Leafcutter Bee and Mason Bee (Megachile): The leafcutter bee cuts sections of leaves or petals to create cell divisions within their nests. They have wide heads and large mandibles (for cutting). They typically nest aboveground in wood with pre-existing holes. They carry pollen under their abdomen (instead of their legs). Mason bees use mud or other “masonry” products to construct their nests in naturally occurring cavities. Some species prefer to use hollow stems or holes in wood as their nest location. In each hole/tube, the female bee lays an egg on pollen and nectar and puts a mud partition between each egg. When the nest is filled the bee will cap the end with mud and look for another nesting place.
Bumble Bee (Apidae): Bumble bees are the furry, round bees often seen buzzing around garden flowers. They are one of our most effective crop pollinators. Bumble bees are social ground bees that build a colony of workers. The queen bumble bee hibernates over winter and starts a new nest each spring. These bees build their nests above the ground using leaf litter or already existing holes or stumps. The queen pulls wax (made from a special gland on her abdomen) and makes a pad to lay her eggs on. She stores pollen and nectar for the larvae feed on. The first brood of workers helps gather more pollen and nectar to increase the supply while the queen lays more eggs. The next generation of queens finds a safe place to hibernate for the winter and the original queen and colony will die by the end of fall.
Yellow Jacket Wasp (Vespidae): These are not bees, but included here for comparison. Yellow jacket wasps consider the ground a potential nesting site, but will also use attics, trees, shrubs and burrows to make their paper nests. They make layered nests from a pulp of chewed up wood fiber and saliva. As noted, the yellow jacket wasp is not a bee, and can be very aggressive and will defend their nests. Use caution around these insects as some people can have a reaction to their stings and bites. These wasps usually have a larger entrance hole (1 inch or more) and there will be many wasps coming and going from the nest.
Written by Joselynn Tokashiki Engstrom, former DNDA Urban Forest Restoration Intern