The Bees in Your Backyard
It is said that one in three bites of food we take requires the work of an insect pollinator. Apples, strawberries, blueberries, cranberries, pumpkins, flax, canola, sunflower and alfalfa need insects to produce fruit or seed. Honey bees, integral to commercial agriculture, are the most familiar pollinators, but are just one of the over twenty thousand bee species found around the world. Four thousand of these bee species are found in the U.S. and Canada. The honey bee, apis mellifera, is not native to the U.S. and was brought to this country by the early colonists. The diminishing of honey bee populations and subsequent concern for agriculture has been in the news, but the importance of our native bees to pollination and the dangers facing them are less well known. To learn who our native bees are and what we can do to protect them, we should start at the beginning.
One hundred thirty-five million years ago, the landscape was covered with forests, ferns and conifers. These plants reproduced by scattering their pollen with the wind. Some insects began feeding on this pollen and, carrying it on their bodies, helped move the pollen from plant to plant. Eventually, plants such as water lilies and magnolias began to develop petals to advertise their pollen and attract pollinator helpers, probably beetles. Over millions of years, flowers created nectar and developed bright colors, shapes and scents to attract the pollinating insects. Evolving along with the plants, the pollinating butterflies, beetles and flies developed the mouth parts needed to suck up the nectar. Bees became the most highly specialized of these pollinating insects and today stand out as the champions of all the insect pollinators. The Beguiling History of Bees.
Is it a bee, a wasp or a fly?
Wasps, which include the fearsome yellow-jackets and hornets, are carnivores and feed on grubs or other insects. They can be aggressive and that painful “bee sting” you have received has most likely come from a variety of wasp. Wasps are very thin between thorax and abdomen (the “wasp waist”), sleek and hairless, with long, dangling legs. They flit in and out of a flower without lingering and might swarm your picnic, lapping from a soda can or taking a bite from an apple. Bees, which evolved from the first wasps, are vegetarian and feed on the sugar-rich nectar and protein-rich pollen found in flowers. Bees are docile creatures and only the female has a stinger. Far too busy sipping nectar and collecting pollen to feed her young, she is unlikely to sting. Bees are typically hairy on body and legs, (to enable pollen to stick) and can spend a long time rummaging around in a blossom looking for the pollen. Flies are also found sipping nectar on flowers. Some, like the hover fly that gathers on asters in the fall, have evolved to look much like a bee, but close observation reveals big differences. Flies are smooth with no pollen-collecting hairs, they have two wings, short antennae, a thick waist and large eyes facing the front of their head. Bees have long, slender antennae, four wings, a distinctly separated thorax and abdomen, pollen-collecting hairs on legs or belly and eyes on the side of the head.
Native bees are considered a “keystone” species, meaning they are central to the food web of an ecosystem, and the survival of many other species depends upon them. By collecting pollen to feed their young, native bees are moving the pollen from flower to flower, allowing the plant to make seeds and reproduce. The seeds and fruit that develop, and the insects that feed on them, are in turn eaten by other wildlife, from songbirds to bears.
Lifestyle of native bees:
Bees go through complete metamorphosis: egg, larva, pupa and adult. Unlike butterflies and moths, the larvae stay in the nest over the winter, only emerging as full-gown adults in the spring and summer. Seventy-five percent of native bees are solitary, meaning the female constructs and provisions the nest on her own. The female mates, makes a nest, lays eggs and provisions the nest with pollen. The larvae hatch, consume the pollen and then, as adults, emerge to start the cycle again. Bumble bees, on the other hand, are social, living in a colony with a division of labor. Whether solitary or social, bees nest in the ground, in hollow stems, abandoned beetle tunnels or in cavities in wood.
Identifying native bees:
Bees are a diverse species, ranging in size from very tiny (smaller than a mosquito) to very large, up to an inch or more. They can be drab brown or reddish; they can be metallic green, blue or black; they can sport white or yellow stripes and can be stout and burly or small and thin. Their legs can be hairy or smooth and their antennae and be long or short. Some have long tongues that can reach deep into tubular flowers; others are short-tongued and feed on shallow blossoms. Given this diversity, how can gardeners identify the bees that flit from flower to flower in their garden? Even bee scientists often inspect a specimen under a microscope to determine the exact species. But by knowing which ones we are likely to see in our Virginia backyards, we can start making educated guesses. Native and Solitary Bees of Virginia.
Mason bees (Family Megachilidae, genus Osmia) are small, up to ½ in length and are colored metallic green, blue or black. Look for them early, as they are among the first to appear in the spring. They carry their pollen on the hairy undersides of their abdomen rather than on their legs. While most are generalists and can feed on many kinds of flowers, some specialize in flowers of the rose or Rosacae family. Apples, cherries, plums and almonds are in this family so if your ornamental cherry or crabapple tree is humming in the spring, you are probably hearing mason bees doing their work. Osmia lignaria, the blue orchard bee, has become an efficient commercial pollinator of orchard crops. Blue orchard bees visit more flowers per minute than honeybees and can fly at lower temperatures than honeybees so can start earlier in the morning, allowing a longer “work day”.
Bees are often named according to the way they build their nests. Mason bees establish their nests in old beetle tunnels, in hollow stems of plants or in holes in wood. The female emerges in the spring, finds a suitable nest and lays eggs in a tunnel, separating each cell with a wall of mud (hence the name “mason”). Before sealing it, she provisions each cell with pollen, which is eaten when the larvae hatch. The saying “busy as a bee” is an apt one. It takes from 15 – 35 trips, visiting as many as 75 flowers each trip, to get enough pollen for one cell and a female may lay eggs in several nests in her short lifetime. The larvae and the hatched bees spend the winter in the nest, finally chewing through the mud in the spring to emerge, mate and start the cycle again. Because mason bees nest in previously built tunnels, you can attract masons to your yard by drilling holes in a block of wood or old stump to provide nesting places. Leave the dried stems of plants standing in the garden through the winter to protect bees who might have taken up residence.
Sweat bees (family Halictidae, genus Lasioglossum) are small, ranging from a few centimeters to one-half inch. Usually metallic, they can be dark brown, black and even shiny green. Often attracted to the salt in human sweat, this is the little bee you might find licking moisture off your arm. These little beauties fly from early spring through fall and are the most commonly seen bee in North America. Because they are generalists, foraging on many flowers, and are abundant in number, they are excellent pollinators. Their small size enables them to go deep into small flowers, making them efficient pollinators of many wildflowers, sunflowers and other composite or daisy-like flowers. They carry their pollen on scopae on their hind legs. A diverse group, they have varied nesting and behavioral habits. Most are solitary, nesting in old insect tunnels in the ground or in decaying logs. Some are semi-social and share nests with other females, creating side chambers that wind around and connect.
Mining bees (family Andrenidae, genus Andrena) are small to medium-sized bees, moderately fuzzy and typically are gray or brown. They are ubiquitous across North America with roughly 550 species occurring in the U. S. Able to tolerate cold, Adrena are among the earliest bees to appear in the spring and can be effective pollinators of crops that bloom early, before honey bees are active. Some species of Adrena are important pollinators of commercial crops such as blueberries, cranberries and onions. Maples (Acer) and Willows (Salix) are among the early blooms visited by Adrena. Species that emerge later forage on sunflowers, blanket flowers, coneflowers and black-eyed susans. As indicated by their name, mining bees nest in the ground, often preferring the bare soil under shrubs or at the base of rocks. A small mound of soil at the entrance to a hole indicates the possible home of a mining bee.
Leafcutter bees (family Megachilidae, genus Megachile) comprise over 130 species throughout the U. S. They are medium in size, ranging from about one-half to almost an inch in length with stout, blackish bodies. Megachile are solitary, with each female building and provisioning her own nest. Most nest above ground in cavities of wood, dead plant stalks, between rocks or in man-made areas such as holes in concrete. The name “Megachile” means “large-lipped” and refers to the large jaws they use to cut sections of leaves they then use to line their nests. Don’t panic if you see large, round holes in the leaf of your plant. It may be the work of a Megachile gathering material for her nest. The female cuts a circular piece out of a leaf and takes it back to her nest where she chews it until gummy. She presses the leaf edges against the walls of her nest, creating a cell which she then fills with pollen before laying an egg in it. The baby bees pupate in isolation, emerging as adults in the summer, ready to feast on a variety of flowers. They carry pollen on the hairy undersides of their abdomens. While many Megachile are generalists, some specialize in flowers of the sunflower and aster families. The alfalfa leafcutter bee (Megachile rotundata) is an important pollinator of commercial alfalfa crops.
Carpenter bees (family Apidae, genus Xylocopa) are the largest native bee, often reaching one inch in length. Because of their size, carpenter bees are often confused with bumble bees, but it is easy to distinguish between them. While the carpenter bee can have a hairy thorax, the give-away that you are looking at a carpenter is its shiny, nearly hairless abdomen. Xylocopa means “wood-worker,” describing their ability to chew holes in wood to make their nests. They can be a nuisance to homeowners when they use their powerful mandibles to drill into the unpainted wood of decks, fences or buildings to establish their nests. They live a solitary life-style, but the males can be territorial, patrolling the nest to deter predators. This can be disconcerting to humans, but like all male bees, male carpenter bees cannot sting. While bothersome, they are harmless. Because they are so large, you will find them foraging on open flowers such as sunflowers. Too big to penetrate tubular flowers like beardtongue and salvia, they can “rob” the nectar of these blossoms by chewing a hole in the base of the flower and drinking the nectar. Even with their robbing tendencies, Xylocopa pollinate crops such as blueberries, tomatoes and melons.
Bumble bees (family Apidae, genus Bombus) are our most familiar and best-loved bee. Bombus comes from the Greek word “bombos” meaning “buzzing sound” and their low, droning, hum is one of the signature sounds of a summer day. Large and furry, bumble bees are distinguished by the black and yellow color patterns on their thorax and abdomen. Bumble bees live a social life style, meaning the queen, sterile female workers and males (drones) live in colonies and have a division of labor. The mated queen hibernates, emerging in the spring to establish her new nest. Most bumble bees nest in the ground in old beetle tunnels, rodent holes or other pre-existing cavities. The queen collects pollen and lays eggs, then stays in the nest as the larvae develop and become adult workers who take over the foraging. The queen lays more eggs which develop into more workers. By the end of the season, the eggs develop into males and a new set of queens. The males and the queens leave the nest, mate, and then the male dies. The workers and old queen also die. The mated queens then find a place to hibernate and the cycle begins again. It is hard to know who is whom among bumble bees, but the time you see them gives a clue. Females fly in early spring; workers fly in spring, summer and fall; new queens and males fly in late summer and fall. With fuzzy coats that help them endure cooler temperatures, bumble bees appear early in the spring and stay active well into the fall. They can raise their body heat to flying temperature by contracting their flight muscles without flapping their wings and warm up by basking in the sun. Bumble bees are generalists, feeding on many flowers and some species have long tongues that enable them to reach down into long tubular flowers. A bumble bee can carry half its body weight in nectar and pollen.
Bumble bees can “buzz-pollinate” by grabbing the flower and vibrating their flight muscles to dislodge the pollen, making them important pollinators of greenhouse tomatoes. They are also pollinators of apples, cherries, blackberries and blueberries.
Bee species can be difficult to identify. But the large, slow-moving bumble bee, with its distinguishable yellow markings, is easier to study. The next time you are in your garden, take a moment to watch these fascinating creatures and see how many you can identify, Bumblebees of Virginia .
While most bees are generalists, feeding on a wide variety of flowers, about 20% are specialists and feed on one, or in some cases, two or three kinds of plant. Specialists are active only when their plant is in bloom, and with only one brood, have smaller populations than generalists. Many specialists rely on spring ephemerals, such as spring beauty, violets and trout lily. Redbud (Cercis canadensis), Dogwoods (Cornus, especially osiers and silky), Winterberry (Ilex verticillata) and Willow (Salix) are important to specialists. Later in the season, flowers in the Solidago and Helianthus families are used by specialists. Specialist Bees Need Special Plants.
One of the most-familiar of the specialist bees is Pepanapsis pruinosa. If you grow zucchini, butternut, pumpkins or other squash, you may have seen these “squash bees” deep in the flowers doing their job. Squash Bees
Bees in decline
Many species of bees have been in decline in recent years, with bumble bees suffering severe loses. There are 14 species of bumble bees in Virginia but many populations have suffered declines — as much at 90% over the past 15 years. Some species of bumble bee, like the rusty patch, are believed to be nearly extinct, and others are rarely seen. The most common, the Common American Bumblebee, is now seen less often. T’ai Roulston and researchers at U.Va.’s Blandy Experimental Farm have been studying the decrease in bumble bee populations and blame the decline on loss of habitat due to urbanization, pesticide use, changing climate and disease. Plight of the Bumble Bee They have found that, assumptions to the contrary, bumble bees can and do thrive in urban and suburban habitats. Unlike rural farms, which go through periods when nothing is blooming, homeowners plant flowers, offering bees the food they need throughout the season. Considering a recent U. N. Report warning of a decline in the health of ecosystems and an unprecedented acceleration of species extinctions, can the home gardener play a role in defending some species? As we garden, why not be intentional about creating the habitat and planting the flowers that will attract and sustain bees? Even the smallest plot in a townhome or balcony in an apartment offers an opportunity to create a bee-friendly environment:
- Plant a variety of blooming trees, shrubs and flowers that bloom from early spring through late fall to attract the specialists as well as the early and late populations. Avoid frilly cultivars with double petals that make access to pollen, if it even exists, difficult. Opt for “open pollinated” varieties of annuals. Most importantly, add as many native species as you can. Native plants are well-adapted to your climate and soil, support bees, and provide nectar and serve as host plants for butterflies and moths. Redbuds, blueberries, coreopsis, coneflowers, Joe Pye weed, liatris, bergamot, asters, penstemon and goldenrods are easy-to-grow natives, readily available, and loved by bees. Find the right plants for your garden by referencing the lists below.
2. Cluster flowers in large groups to make foraging easy. A bumble bee can fly up to a mile, but a small bee may only venture 500 feet from its nest.
3. Provide nesting and overwintering sites by leaving some areas mulch-free and leaving dried stems of perennials and grasses standing throughout the winter.
4. Do not use pesticides. Systemic pesticides, such as neonicotinoids, are not selective and infiltrate all parts of a plant, including stems and leaves, making the whole plant toxic. Some greenhouses and nurseries treat young plants with “neonics” before sending them to garden shops, so it is wise to check before purchasing. To learn more about neonicotinoids, read the recent article in “The Garden Shed,” Another Pesticide Controversy: Neonicotinoids and Pollinator Decline
Gardeners love the beauty, scent and sounds of a garden. Now consider making it exciting by inviting the bees. When you start feeding the bees, you’ll find that butterflies, dragonflies, moths, hummingbirds and other fascinating creatures will soon take up residence. As your garden hums with life, you will also be invited to spend more time in the garden as it becomes a vibrant, beautiful ecosystem for all to enjoy.
References and more information:
The Bees in Your Backyard: A Guide to North America’s Bees (Wilson, Joseph S. and Carril, Olivia Messsinger, Princeton University Press, 2016)
Our Native Bees (Embry, Timber Press, 2018).
Attracting Native Pollinators (Xerces Society,Storey Publishing, 2011)