Who’s that pollinating my garden?
It happens to nearly every beekeeper. You plant an array of flowering plants — from annual poppies to honeysuckle vines to crabapple trees — all tenderly selected to entice your darlings to forage. On the first balmy spring day, you watch your bees missile out of their hive and into the blue, but when you stroll through your garden, there’s not a honey bee in sight.
As you walk among your plantings, wondering where your bees went, you catch sight of the imposters — insects flitting from blossom to bloom, doing what your girls ought to be doing. But who are these guys? All you can say for sure is they’re not honey bees.
Learning how to identify the pollinators in your garden is no easy task. Even those who’ve spent years learning can have difficulty nailing it down without a dissecting scope and a teetering pile of reference books. What makes it so difficult?
Honey bees are outliers
Keepers of honey bees seem to be particularly confused about other species, and the reason is simple. Honey bees are outliers in the bee world, meaning many of the things you’ve learned about honey bees do not pertain to other bees in your garden. Even though all bees basically do the same thing, they do it in different ways.
For starters, let’s look at seasonality. You see your honey bees on the first flying day of spring to the last flying day of fall and every day in between. But other bees are different.
In spring and summer, adult bees have a life span of about four to six weeks. This holds true for just about any species. But since honey bees live in a colony that persists from year to year, bees that die are continually replaced by a busy queen. However, most wild species emerge at a particular time, reproduce during their allotted four to six weeks, and then die. Since their offspring won’t emerge until the following year, the species disappears from your view.
Different species begin to emerge at different times of year. Some appear in February, March, April and so on throughout the season. They do their reproductive thing, then disappear. From a human standpoint, that means the assortment of bees in your garden is different in April than it is in June or August. In fact, if you inventory the bees in your garden every single week, each successive week will look slightly different from the one before.
The limits of foraging distance
Then too, many of the wild species have very short foraging ranges. Mason bees (genus Osmia) may fly 200 to 300 feet at most. Compare that to a honey bee who, when push comes to shove, can cover five miles or more. Among other things, that means that your neighbor may have an entirely different selection of bees, some that never enter your yard. And certainly the list of California girls is different from the roster of Jersey girls.
Time of day matters, too. Some species forage early in the day, and some forage late or even at twilight. Some wait for the air to warm, some go to shelter when the sun gets too hot. Climate matters. Altitude matters. Flora matters. Simply put, the bees in your garden are the ones suited to your particular microclimate. And when that microclimate changes, the bees change along with it.
Hazards to identification
Then there is the difficulty of identifying bees, even when they hold still. Honey bees are drop-dead easy. Of all the bees in the genus Apis, only one species, Apis mellifera, is found in the western hemisphere.
Compare that to the mason bee genus Osmia. North America alone has more than 140 species of Osmia. Some of these can be distinguished with a good macro photograph. Others, perhaps most, need to be dissected and measured and compared with collected specimens. It turns out that the most telling parts of bees are the penis shaft and the mouthparts, both hard to see in a live bee, even if they were willing to drop their drawers or say “ahhh.”
And let’s not forget size. It’s hard to identify something you can barely see. The smallest bee in North America is about 2 mm long. In inches, that’s about one-sixteenth, or the thickness of US nickel.
Other bee-like insects
Before you can identify a bee, you first need to eliminate the insects that are commonly confused with bees. Usually, that means flies and wasps. I have seen drone flies in the pages of bee magazines, on the covers of bee books, on bee websites, and in bee newsletters. It’s odd because, although these flies mimic honey bee drones and look somewhat similar, how often do you see drones foraging on flowers? You don’t. So foraging behavior should be a colossal hint. Remember, if you see a drone rummaging through the dandelions, look twice. Flies have stubby little antennae and do that hand-washing thing: easy peasy.
Wasps are harder to distinguish, but since they don’t collect pollen, they have little hair compared to bees. Male bees and cuckoo bees don’t collect pollen either, and Hyleaus bees swallow it, so there’s plenty of room for confusion. Technically, bees have branched hairs somewhere on their bodies, and wasps don’t, but that’s not something you can see at a distance.
Interactions with the environment
Oftentimes, identifying a bee begins by watching it interact with its environment. For example, does it nest in the ground or in a tiny cavity? Are similar bees nesting nearby or is your bee alone? Since you won’t see spring bees in the fall or vice versa, the season is a great clue.
And most telling, perhaps, is how it carries pollen. Is the pollen on legs or abdomen? If legs, is it packed tightly in a corbicula (like a honey bee) or is it loose and fluffy? Is the pollen restricted to the tibia or is it also carried on the femur and trochanter? Or perhaps along the sides of the abdomen but not underneath? Some carry it on the back of the thorax and some carry on the midlegs as well.
Then too, the flowers it visits offer a clue. For example, many of the specialist Andrena mining bees that collect pollen from a single type of plant can be distinguished by the plants they visit. Believe it or not, there is a trout lily mining bee, a spring beauty mining bee, a waterleaf mining bee, and an aster mining bee. Identification by circumstantial evidence is often correct.
Genus level IDs are fine
Beginners at bee identification have an inexplicable urge to classify them down to species level, even if they aren’t sure. Those with more experience realize that, unless you are doing a formal survey of biodiversity, naming the genus is usually good enough. With an estimated 4000 species in North America alone, a quest for species-level identification can be discouraging. But if you can tell a Colletes from and Trachusa from a Calliopsis, you can pat yourself on the back.
To make the beginner’s job even more difficult, many of the bees don’t have common names. That said, during the last few years, taxonomists have made a heroic effort to assign common names whenever possible, simply because they are easier to remember. Unfortunately, many of these names are back constructions derived from the scientific name. So now we have strange monikers like the miserable mining bee (Andrena miserabilis) and the frigid bumble bee (Bombus frigidus). Not very helpful.
Unfortunately, even logical-sounding common names are not a panacea. For example, the two-spotted longhorn bee doesn’t always have two spots, nor do the females have long “horns.” The brown-belted bumble bee doesn’t always have a brown belt, and the orange-tipped digger bee may be missing an orange tip. And although I can identify a ligated furrow bee and an unequal cellophane bee, I have no idea what makes them ligated nor unequal. Go figure.
Nothing short about it
For all these reasons and more, I cannot possibly write a 2500-word guide to identifying the bees in your garden. But in order to help a wee bit, I selected some of the bees most commonly sent into iNaturalist.org for identification. At iNaturalist you can upload photos of anything from a fungus to a mountain lion and have it identified by a worldwide network of citizen scientists. The bees shown there tend to be the largest, most colorful, and easiest to photograph — the very reasons they get submitted in the first place, so it’s a good place to start.
I divided the continent into east and west — not a fine division for sure, but I could find very few species that live in most states and provinces. The bee I will start with is a rare exception: the orange-legged furrow bee, Halictus rubicundus.
For the last dozen years, I’ve been calling the orange-legged furrow bee “America’s premier pollinator.” Not only is it found in all the lower 48 states and most Canadian provinces, but it is found in all types of agricultural crops, natural landscapes, and in widely varying climates. It is small enough that most people either don’t notice it or think it’s just a small nondescript bug, but it’s been known to pollinate hundreds of plant genera and thousands of species. If you have a garden or farm in North America, you likely have orange-legged furrow bees.
Common eastern bees
The common eastern bumble bee, Bombus impatiens, ranges from Ontario to Florida and as far west as Wyoming. This large yellow and black bee is highly adaptable to different environments, which makes it one of the most important pollinators of agricultural crops. In the U.S., this species is used for commercial bumble bee production, so it is often found beyond its natural range. It is often confused with the brown-belted bumble bee, Bombus griseocollis.
The eastern carpenter bee, Xylocopa virginica, is an exceptional pollinator that is frequently considered a household pest. Large carpenter bees have the disconcerting habit of boring holes into milled lumber. Sacred parts of your house, such as fascia boards, may become riddled with tunnels if they are not painted. Oddly enough, the eastern carpenter female lays eggs that are a little over half an inch long — one of the largest eggs in the insect world.
I included the introduced sculptured resin bee, Megachile sculpturalis, on this list because of its ability to strike fear in the hearts of beekeepers. This large, scary-looking bee will often attack a carpenter bee and kill it by smearing it with plant resin. Beekeepers witnessing this behavior often fear the resin bees will go after their honey bees next, but not so. The resin bees are simply trying to appropriate the custom-made nesting tunnel of the carpenter bee, something honey bees can’t provide.
The bicolored striped sweat bee, Agapostemon virescens, is one of 43 species of striped sweat bee found in North America. Both sexes have a glittery green head and thorax, but in this particular species, the males have a black-and-yellow striped abdomen, while the female abdomen is black and white. The striped sweat bees are prodigious pollinators of many plants, but they are especially fond of the sunflower family.
If you grow any cucurbits in your garden — squashes, pumpkins, or cucumbers — you may very well see the pruinose squash bee, Peponapis pruinosa. These bees have wide black and white stripes on a flattened abdomen, and are frequently seen in groups working deep in a squash flower. The females go foraging at first light, just when the squash flowers open. After the flowers wilt in mid-morning, you can often peel apart the collapsed petals to find the males sleeping inside.
Another solitary green bee is the pure green augochlora (Augochlora pura). Unlike the bicolored striped sweat bee, the pure green augochlora is one color from stem to stern, although that color may range from green to blue, sometimes with coppery highlights. This bee is unusual because it nests in rotting wood in damp environments and can produce up to three generations per year. Like most of the sweat bees, it forages on a wide variety of plants.
Common western bees
The urbane digger bee, Anthophora urbana, is another quick and noisy bee. They have robust bodies, broad heads, large scopae on their rear legs, and brilliant blue eyes. These ground nesters are incredibly fast, producing many blurry photographs. Urbane diggers are bivoltine, meaning they produce two generations per year.
Frequently seen along the west coast from Alaska to northern Mexico is the black-tailed bumble bee, Bombus melanopygus. One of the first bees of spring, the queens often emerge as early as January. This species is at home in an urban environment and has the endearing habit of nesting in mailboxes, bird houses, compost piles, and discarded mattresses. Or, if none can be found, a hole in the ground works just as well. One form of this bee is black and white, while another form has a bright orange band across the abdomen. Both are excellent pollinators of crops and wildflowers.
Like introduced plants, introduced bee species have few natural enemies, so they tend to spread quickly. The charismatic European wool carder bee, Anthidium manicatum, is no exception. This bee is large, noisy, and extremely territorial. The male stakes out a patch and defends it against interlopers by hovering and watching. If an intruder comes too close, he will be met with a set of daggers mounted at the end of a yellow-and-black stripped abdomen. While the male wool carder keeps watch, the female can often be seen scraping fibers from furry stems and leaves which she uses to line her nests.
Osmia lignaria propinqua is the western subspecies of the blue orchard bee. These native bees are often raised for pollinating early spring fruit trees, a practice that has greatly expanded their range. Often referred to simply as “mason bees,” they nest in tubes which are easy to transport. In addition, the tubes can be refrigerated until needed, thus giving the orchardist some control over emergence times. Blue orchard bees are efficient pollinators of many early crops.
Leafcutters are the show-offs of the garden, reminding me of gymnasts and ballerinas, with postures that seem to shout, “Look at me!” The western leafcutting bee, Megachile perihirta, is one of the larger leafcutters and one of the hairiest. The males have long fringy hair on their forelegs which they use to cover the eyes of their partner while mating. Like most leafcutters, they line their brood cells with round pieces of leaves and petals, but unlike most species, the western leafcutter nests underground in shallow tunnels. When hunting for leafcutters, look for bees that hold their wings out to the side while foraging.
Although the prunus mining bee, Andrena prunorum, is known for pollinating apple and onion blossoms, it also will pollinate a large selection of other early-season plants. They carry pollen high on their rear legs and on the backs of the thorax, often filling the space between thorax and abdomen. Like all Andrena, they have large basitibial plates that look like bare kneecaps poking through the pollen load. The prunus miner is a solitary ground nester with distinctive orange wings and legs.
A reason to learn
Learning to identify and appreciate the pollinators in your garden adds another dimension to your life with bees. When you recognize wild species and understand how they compare and contrast with honey bees, you become a better, more nuanced beekeeper. So take a closer look and discover who is really pollinating your garden.
Honey Bee Suite
Special thanks to photographer and naturalist Robert Noble of Brampton, Ontario for his photos of eastern bees and his help in selecting species to highlight. See more of his work at BobNoblePhoto.wordpress.com.