Native Bees of North America
Native bees are an unappreciated treasure, with 4,000 species from tiny Perdita to large carpenter bees, they can be found anywhere in North America where flowers bloom. Most people don’t realize that there were no honey bees in America until the white settlers brought hives from Europe. These resourceful insects promptly managed to escape domestication, forming swarms and setting up housekeeping in hollow trees, other cavities or even exposed to the elements just as they had been doing in their native lands. Native pollinators, in particular bees, had been doing all the pollination in this continent before the arrival of that import from the Old World. They continue to do a great deal of it, especially when it comes to native plants.
Non-native honey bee, Apis mellifera: 1. Queen surrounded by attendants. 2. Swarm. 3. Combs of a feral colony
The honey bee, remarkable as it is, doesn’t know how to pollinate a tomato or an eggplant flower, while some native bees are masters at this. The same thing happens with a number of native plants, such as pumpkins and watermelons, blueberries and cranberries, which are more efficiently pollinated by native bees than by honey bees. Let us take a closer look at this forgotten treasure of native bees.
Native bees come in a wide range of sizes; they are also varied in their shapes, life styles, places they frequent, nests they build, flowers they visit and season of activity. They remain unnoticed by most of us and yet they provide valuable services to all kinds of flowering plants, from wild flowers to some important crops. For instance, the Southeastern blueberry bee is a hard working little creature, capable of visiting as many as 50,000 blueberry flowers in her short life and pollinating enough of them to produce more than 6,000 ripe blueberries worth about $20 at the market. Not every bee that you see flitting about may be worth $20 but all of them combined keep the world of flowering plants going; flowering plants are a key component of most land ecosystems.
Bees are descended from wasps. Most wasps are carnivores; they either prey upon or parasitize other little creatures, mostly other insects, and use this rich protein source to feed their babies. Many millions of years ago, when the first flowering plants begun to bloom, some wasps made a switch from hunting prey to gathering pollen for their brood. Perhaps they were hunting for insects that visited flowers and ate some of the pollen along with their prey. It didn’t take much to find the advantages of consuming pollen over hunting. Pollen is also rich in proteins and doesn’t fight back so it is easy to imagine why they were happy to become vegetarians. Gathering pollen and nectar requires certain adaptations different from those of hunters; so they started to change to meet these requirements and consequently became bees.
Most bees have very furry bodies and the hairs are feathery, better for trapping loose pollen. If you observe bees or bumble bees visiting flowers you will notice that some are totally covered by pollen grains.
1. Pollen covered Diadasia. 2. Plumose hairs (trapping pollen grains)
However, this would not be a very convenient way for transporting their cargo back to the nest, so most have pollen baskets of one sort or another, either on their hind legs or under their bellies. They frequently brush themselves, picking all those loose pollen grains and transferring them to their pollen baskets. They have a fairly long tongue to sip the nectar usually buried in the heart of the flower, and a large crop or a second stomach for carrying it. A few less visible adaptations took place also when bees were evolving from wasps, including a knack for finding flowers through smell, colors and patterns and a good memory to keep going back to the same flowers that yield a good recompense.
1. Tibial scopae of Agapostemon virescens. 2. Abdominal scopa of Megachile centuncularis. 3. Corbiculae of Bombus impatiens
The mother bee uses some of the nectar to mix it with the pollen. She also uses it for her own nutrition; nectar is a high octane fuel and with all the flying she does she needs a lot of fuel. In this respect bees resemble many of their relatives, the wasps.
All bee families have species that take care of their young by building nests and providing food for them. But several families, such as Apidae, Halictidae and Megachilidae have some black sheep, some selfish species that take advantage of their relatives. They have become “cuckoos”, just like there are cuckoos among birds. As with cuckoo birds they lay their eggs in the nests of others. Their babies feed on the stored food and also on the larvae of the unfortunate hosts. Cuckoo bees don’t need to gather pollen and have lost their pollen baskets and much of their hair, in fact, at first sight some of them are often mistaken for wasps.
Aside from cuckoo bees, all bees build nests, stocking them with a nutritious mixture of pollen, nectar and saliva before laying their eggs, and usually sealing them so the babies remain safe. They generally mix the dry pollen with some nectar kneading it into a bee loaf, used to feed their children. They add their own saliva to this mixture. The saliva seems to be an important ingredient that confers some protection against bacteria and fungus infections.
Some build their nests underground, others use hollow stems or holes in trees, perhaps left by beetles, others use their powerful jaws to make holes in wood. Be as it may they start the job of nest building by carefully choosing the best real estate; if conditions aren’t right they continue their search. It wouldn’t do to have their homes flooded or lacking enough sunshine, or being too large or too small for their needs.
Miners
Many members of the larger families, Apidae, Andrenidae, Halictidae, Megachilidae and Colletidae are ground nesters. They choose a bare spot, with sunshine and not likely to get flooded, and start the task of digging that may take several days. They build a long tunnel slightly wider than their own bodies. Some don’t want any neighbors around; on the other hand, others prefer the company of their own sisters. They may make little towns or even large towns; but they still remain solitary in the sense that each digs her own nest and takes care of her own brood all by herself. Still others show different levels of cooperation, sharing the tasks of nest building and food provisioning. This tunnel can be a foot long or even longer. It may twist halfway or take a turn near the end. At the end of the tunnel the mother bee builds a chamber a little wider; this will be the nursery for just one baby. She fills it up with enough food for one bee to grow from egg to full size. There she lays an egg and seals the chamber. She will add other branches to the tunnel; at the end of each there will be another cell or chamber properly stocked and with an egg. Imagine a bunch of grapes; that is what some of those nests look like.
1. Colletes inaequalis at the entrance of its nest. 2. Part of an aggregation of Lasioglossum zephyrum nests. 3. Semisocial Agapostemon virescens sharing the entrance to their nest. 4. Aggregation of Anthophora bomboides nests. 5. Andrena
Hole nesters: masons and leafcutters
Members of several families take advantage of already existing holes; that is, they use hollow stems or holes made by beetles or other agents in trees. There, they construct chambers, usually lined up in a row, which they stock one by one to serve as nurseries.
Most members of the family Megachilidae are hole nesters who use certain materials to prepare the nest properly. Some use clay to build walls between cells and to seal the entrance; therefore they are called mason bees. Others cut round pieces of leaves for the same purpose and also to line the inner walls of the tube; they go by the name of leafcutters. You may have seen those nearly perfect circles missing from the leaves of your rose bushes. Please, don’t begrudge this housing material to such hard working mothers.
1. Megachile albitarsis gathering material for her nest. 2. Young male Osmia cornifrons emerging from nest. 3. Interior of a Megachile xylocopoides’ nest. 4. Megachile sp. sealing nest hole
Carpenters
Other bees use holes of their own making; they have powerful jaws with which they can excavate tunnels in wood. Fortunately they prefer soft wood and dislike paint or other finishing materials; so it is possible to prevent them from doing serious damage to wood structures by taking simple precautions, such as painting or coating any exposed wood. They are called carpenter bees and very likely you have seen some of them and some of their handiwork. There is usually a pile of sawdust below the entrance to the nest.
1. Xylocopa’s nest entrances. 2. Xylocopa virginica at nest’s entrance
Foraging
Some bees are generalists and can use the pollen from a large variety of flowers; but most of them have some degree of specialization and resort to pollen from only a few or even just one kind of flower. However, they may collect nectar from a wider range of flowers in addition to the ones they visit for pollen.
Bombus ternarius visiting different flowers through the seasons
One example of specialization is the squash bee, which is very proficient at visiting flowers of vine crops. A few other examples are blueberry bees, azalea bees, globe mallows bees, which specialize in the mentioned flowers. Some species are active only for a few weeks in the spring and therefore can only use the flowers that are in bloom at that particular time. But others, such as bumble bees, have long lived colonies that start in the spring and last until the fall so they have to keep switching flowers as blooms come and go.
1. Peponapis pruinosa visiting a squash blossom. 2. Habropoda laboriosa on blueberry blossom
Most flowers open their blossoms during the day and produce more nectar and perfume during those hours, so it is not surprising that most species of bees keep the same schedule. However there are a few species in each of the main families of bees that become active only at dawn or dusk; naturally they pollinate those flowers that bloom at such times. They are called crepuscular bees.
In general, when not working, the females rest inside their nests. The males, on the other hand, have nothing to do with nest building or provisioning, so they find other places to rest. Occasionally it is possible to find a cluster of males, clinging by their jaws to flowers or twigs. Squash bee males are frequently found in groups inside the squash blossoms which are beginning to wilt.
1. Cluster of sleeping male Bombus insularis. 2. Male melittid bees, Hesperapis, inside a blossom. 3. Squash bees, Peponapis, in squash blossom. 4. Male Halictus parallelus
The long tongued bees, Apidae and Megachilidae, favor flowers with a longer throat, although they are not averse to sipping nectar from flat open flowers. The remaining families, the short tongued ones, are more limited in their choices and can only take advantage of flowers with easily accessible pollen and nectar.
Long tongues of: 1.Osmia cornifrons. 2. Anthophora abrupta
Families of bees
There are about four thousand different species of bees in North America. The members of the five most common families, Apidae, Halictidae, Andrenidae, Megachilidae and Colletidae can be found throughout the continent from Canada and Alaska to warm and sunny Florida; from forests to deserts; from remote areas to gardens and backyards; even the National Mall in the very heart of our nation’s capital sports a fauna of native bees. Perhaps the only places where bees are absent are the high mountains.
There is even a hardy little soul, the boreal bumble bee, which lives within the Arctic Circle. The young queen starts raising her family when there is still frost on the ground and sometimes she has to spend hours covering her babies to keep them warm. Just like some birds that have a brood patch on their bellies, these bumble bees also have a bare spot to transfer heat from their bodies to their children. Bumble bees and a few other insects are warm blooded animals; they can be real powerhouses that produce energy by vibrating their flight muscles repeatedly. Thus the mother spends long hours shivering to generate the needed heat; this intense effort requires a lot of fuel so she needs to keep sipping honey, an excellent energy source. Finally, after spending long hours taking care of her family, when the sun heats the land, that tired working mother has to leave the nest in search for supplies for the family.
Apidae
This large family includes a wide variety of species, starting with that non-native, the honey bee, Apis mellifera; in fact the name of the family comes from the Latin name for the honey bee, Apis. It includes all the bumble bees, the carpenter bees, several kinds of miner bees and some types of cuckoo bees.
Honey bee: 1. Worker. 2. Comb with some larvae
There are about fifty species of North American bumble bees. Most people are familiar with them; they are big and furry, mostly black with stripes of yellow or white or even bright orange. They have some things in common with honey bees; they are more social than most other bees forming colonies with one queen and many workers, although such colonies are never as big or as long lived as those of honey bees.
1. Bombus affinis. 2. Bombus impatiens. 3. Bombus perplexus. 4. Bombus vosnesenskii. 5. Bombus fervidus
Bumble bees are ground nesters, most make their nests in a cavity; but a few merely build their nests above ground somewhat covered by thatch and debris. The cavities they need for their nests are larger than those of solitary bees, so the first thing that a young queen does in the spring is to find an abandoned mouse nest or a similar burrow. Then it starts insulating it and preparing it for her brood. She builds a few wax pots that she fills up with honey and a larger one which she stocks with a mixture of pollen and nectar and where she lays her eggs, no more than half a dozen at first. They are all sterile female workers; when that batch is fully grown the queen doesn’t abandon the nest again, spending all her time laying more eggs while the workers take care of all the chores in and out of the home. The colony grows rapidly and it can reach as many as a couple of hundred workers although it rarely gets that large. The workers are usually smaller than the queen; that is why you seldom see large bumble bees after the spring. Near the end of the summer the queen lays some male eggs in addition to female ones. The females born at this time become queens, not sterile workers, and they mate soon after they emerge as adults.
All the workers and drones and the old queen die at the end of summer; the only survivors are the new queens, already mated. They find a secluded and safe place to spend the winter and go to sleep; they will start a new colony the next spring.
1. Bombus bimaculatus colony. 2. Bombus impatiens colony
Another thing that bumble bees have in common with honey bees is the kind of pollen baskets, called corbiculae (singular,corbicula), on their hind legs; they are more specialized than the pollen brushes or baskets of other bees which are called scopae (singular, scopa). In honey bees and bumble bees the tibia segment of the hind leg is flattened and has rows of long strong hairs or bristles along the edges of these flattened parts. Thus the shape of these baskets allows them to pack the pollen, mixed with some nectar and saliva into a tight ball rather than the loose mass of pollen grains clinging to the hairs of the scopa of other kinds of bees. A few species of bumble bees have become cuckoos laying their eggs in the nests of other bumble bees. They have no need for workers or for pollen baskets.
Cuckoo bumble bees: 1. Bombus fernaldae. 2. Bombus citrinus
Bumble bees are so good at pollinating tomatoes that their services are put to good use in large green houses that grow tomatoes year round. All that is needed is a queen, a box for the nest and a supply of sugary water because tomatoes produce a lot of pollen but no nectar. The bumble bees are free to come and go but remain content inside the green house most of the time doing their job.
Carpenter bees are also black and large and you may have trouble telling them apart from bumble bees except for one distinctive feature: bumble bees are fuzzy all over, while the abdomen of carpenter bees is almost hairless so it looks rather glossy. Male carpenter bees of some species have a large white patch on their faces. Early in the spring the males establish territories that they patrol and protect zealously not letting other males come near; in fact often they chase away almost anything that moves including unwary gardeners. Sometimes they choose territories near promising nesting sites not because they plan to set housekeeping but because they know that such places will attract females. Fortunately they can’t sting, only females do that, so there is not much to fear and you can let them be. The females have powerful jaws and can dig holes in soft wood to make their nests, hence their name of carpenter.
1. Male Xylocopa virginica patrolling its territory in early spring. 2. Female X. virginica. 3. Female X. virginica sealing the nest entrance
Carpenter bees are not always well behaved pollinators. Occasionally, when a flower has a long throat that places the nectar out of reach, the bee uses her sharp tongue to make a slash at the base of the flower where the nectar is stored. She then drinks it without coming near the pollen dispensing anthers and stigma of the flower. Thus, carpenter bees can be nectar robbers who cheat the flower instead of doing it a service in return for its nectar. Bumble bees and honey bees are also quite capable of this kind of thievery. Look at the trumpet honeysuckles, horse mints or abelias in your garden and you may find the tell tale signs of these attacks.
There are some small relatives of the carpenter bees called small carpenter bees, genus Ceratina, although you would never mistake one for the other because of the size difference. They nest in hollow twigs, or in pithy stems, such as blackberry brambles or roses.
1. Ceratina calcarata. 2. Ceratina arizonensis
One large group within the Apidae family, the Nomadinae, is made exclusively of parasitic bees or cuckoo bees. Nomadinae bees are usually red with whitish markings. They have lost all the adaptations that serve to carry pollen as they don’t need to do so; they are almost hairless and wasp like. Many parasitize the nests of Andrenid bees. They are often seen in early spring flying low, searching for the ground nests of their hosts. When they locate a nest, they wait nearby ready to sneak in and lay an egg while the busy mother, legitimate owner of the nest, goes in search of food. The egg of the cuckoo bee develops rapidly and grows into a larva that will kill and eat the resident baby as well as the food reserves in the nest.
Cuckoo bees: 1. Female Nomada of the luteola subgroup. 2. Female Nomada imbricata inspecting a host’s nest, presumably an andrenid’s. 3. Triepeolus remigatus
Among the miners we can mention some very useful ones such as the squash bee, Peponapis, which pollinates flowers of squash, pumpkin, and other vine crops. They are about the same size and general coloration of a honey bee, but you can easily tell them apart by their behavior when they are near flowers of these crops. They are fine tuned to the daily rhythms of squash flowers so they start their work shift early in the morning when flowers are at their peak. They show no hesitation when approaching a squash flower, plunge right in, briskly collect supplies and leave in a hurry. Honey bees, on the other hand, arrive later at the flowers when they are past their prime; they also take some extra time hovering over the flower and visiting it leisurely. Even with bee hives nearby it is estimated that squash bees do several times more pollination than honey bees. Vine crop growers are very aware of their value as pollinators. These bees usually nest under the very plants they pollinate. If you are one of those who pick up your own pumpkin to make a Jack-o-lantern, you will be walking over some nests full of sleeping young squash bees.
Mating Peponapis pruinosa bees
One spectacular member of this family is a recent arrival from the tropics, the orchid bee, Euglossa, which somehow found its way into Florida; nobody knows how.
Euglossa viridissima: 1. Male with enlarged hind tibiae. 2. Female with corbicula full of pollen
The industrious $20 bee, the blueberry bee, Habropoda laboriosa, mentioned above and many of its relatives, the Anthophorini, belong to this family. They are mostly hairy, heavy set bees with impressively long tongues.
1. Habropoda depressa. 2. Anthophora centriformis
Megachilidae
This family contains the called mason bees and leaf-cutter bees. Most of them nest in holes, either in wood or hollow twigs, but there are also a few that nest in the ground. There are a few species within this family that are not native but have been introduced either intentionally or unintentionally in this country. Among the intentional introductions there is the Japanese bee or horned bee, which is considered an excellent pollinator of fruit trees. One interesting characteristic of the members of this family is that they don’t carry the pollen on their back legs but on their bellies. If you happen to see a bee, about the size of a honey bee, with a yellow belly you can be sure that it is a Megachilid bee.
1. Lithurgus apicalis. 2. Megachile inermis. 3. Cuckoo bee: Coelioxys modesta
The blue orchard bee, Osmia lignaria, and specially the variety Osmia lignaria lignaria of western United States is being developed for pollination of fruit trees by providing nest houses. It may prove to be an excellent replacement for the beleaguered honey bee.
Osmia lignaria
Halictidae
Some of the prettiest bees belong to this family; with their shiny metallic colored bodies they capture your heart. Many are metallic green, but others have shades of color that go from blue to copper or gold. Most of them nest in the ground, some are completely solitary but others share the entrance to their nests. In most cases that is all they share and don’t go to the extent of being truly social. However, a few go a step further and show some division of labor in guarding the entrance to their homes and rearing of the young; they are usually sisters that came from the same nest. Some species go even further in their level of socialization and can be considered truly social, with a division of labor in which the mother and starter of the colony lays eggs and lets the daughters do all the other work.
1. Male Agapostemon splendens. 2. Augochloropsis metallica. 3. Augochlorella sp.
Not all are metallic green; there are some black ones, also. Among these there are some that are solitary while others, such as some in the genus Halictus, are social. They may have from a few to many females sharing family rearing; however, their colonies never reach the complex social structure of those of bumble bees and honey bees.
1. Halictus confusus, nectaring. 2. The social Halictus tripartitus at the nest
One attractive halictid is Augochlora pura (the name means the pure magnificent green bee) found in the eastern United States. She has the peculiar habit of building her nest under the bark of a rotten log. She takes advantage of the loose, half rotten material to make some sort of bedding adding her own saliva and secretions to build an envelope for the larvae and accumulated food. It kneads the pollen into a number of little loaves shaped like tiles, which she plasters on the inner wall of the brood chamber and lays an egg before sealing the cell completely. This precaution is absolutely necessary with all the marauding ants and other hungry creatures that abound under loose bark.
Augochlora pura: 1. Adult females. 2. Nest. 3. Female and larva
A very useful halictid bee is the alkali bee, Nomia melanderi, of western United States. As its name suggests it prefers to build its nest in alkaline terrain. It likes to live in aggregations or colonies, not exactly social since each bee tends to her own brood, but companionably close to each other. It is a very good pollinator of alfalfa and some growers take advantage of its nesting habits to manage this species to some extent. They supply the appropriate terrain for their nesting needs near alfalfa crops even creating it artificially by using tarp, covering it with clay and watering it as needed to create the best conditions.
Nomia melanderi
There are also some cuckoo species in this family and, just like the other cuckoo bees, they are almost hairless and somewhat wasp like. Some have a bright red abdomen.
Cuckoo halictid bee, Sphecodes davisii
Andrenidae
The andrenid bees are all ground nesters. This is a very large family. Many are dark, black, and rather non-descript bees; others have bright red colors. those in the genus Perdita can be quite striking, metallic greenish, or with yellow markings. They can be distinguished from other bees by the velvety areas (fovea) on the face, between the eyes and the base of the antennae. Andrenids are among the earliest bees to emerge in the spring. You can see them visiting violets and other early blooming flowers. Some andrenid bees are very good pollinators of apple blossoms. Many of them are active only during this brief period. The next generation remains sound asleep underground through summer, fall and winter only to emerge the next spring when their favorite flowers are in bloom.
1. Andrena nubecula. 2. Perdita sp. 3. Andrena prunorum. 4. Andrena sp. showing the hairy facial fovea
What would the forests be without azaleas and rhododendrons? Their flowers are the kind that honey bees cannot pollinate. These flowers don’t release their pollen like most flowers, but hold it inside the anthers waiting for some skillful bee that knows how to shake it, just like a saltshaker. Bumblebees and a number of solitary bees are good at this; the Cornell azalea bee (Andrena cornelli) is one of them, a dark colored, slender bee which is found in the eastern United States. It is never too far from azaleas or rhododendrons because their pollen is its favorite food. Besides being very competent at shaking the anthers, her pollen baskets with long widely spaced hairs, are especially adapted to the particular clumpy texture of these flowers’ pollen.
Andrena cornelli
Colletidae
This is a small family sometimes considered as more primitive than other bees because their tongues (glossa) are broad and wasp-like. Some colletids, the yellow-masked bees, such as Hylaeus, don’t even have baskets to carry pollen so they have to carry it inside their crops. They are not as hairy as other bees and can easily be mistaken for wasps. Many are ground nesters; sometimes forming large aggregations. Those in the genus Hylaeus don't dig nests but use available cavities such as hollow twigs. The members of this family use a cellophane-like material to line the chambers where they lay their eggs; so sometimes they are called cellophane bees.
1. Colletes hyalinus. 2. Hylaeus sp. 3. "Cellophane" lined cell of a colletid bee
Melittidae
Finally, there is an even smaller family of bees, the melittid bees, represented by only a few species. Most of them use pollen from just one species or a few species of plants. Some also use floral oils to feed their brood. According to recent DNA studies, this family rather than Colletidae would be the basal branch of bees, or the most primitive.
Hesperapis regularis
Bee mimics
Last but not least, let us mention those superb impersonators of bees, certain flies which are frequent flower visitors, in particularSyrphid or flower flies, bee flies and a few robber flies. Don’t be fooled by them, despite their appearance they are not bees but flies; they don’t have a sting as bees do, so they masquerade as bees to fool hungry birds. Often they succeed at fooling the inexperienced observer of bees, too.
They have only one pair of wings instead of two. This is a very significant difference but nearly impossible to notice when they are flying about. Part of the reason for this difficulty is that bees’ wings have tiny hooks that lock the front and hind wings together making them appear as just one. There are several other differences that would be more helpful to the observer of living flower visitors such as bees and flies. These flower visiting flies have huge eyes, very short antennae and skinny legs when compared to bees.
Syrphid flies: 1. Toxomerus marginatus. 2. Eristalis tenax. 3. Mallota bautias. Beefly: 4. Bombylius major. Robber fly: 5 Laphria thoracica
Additional readings
References in Anthophila, at the bottom of the page.
Goulson, Dave (2003). Bumblebees, Behaviour and Ecology. Oxford University Press, Oxford OS2 6DP ISBN 978-0-19-852607-0
O'Toole, Christopher, Raw, Anthony (1999). Bees of the world. Cassell Illustrated. ISBN 0-8160-5712-5
Mader, E., Shepherd, M., Vaughan, M., Black, S. H., LeBuhn, G. (2011). Attracting Native Pollinators. The Xerces Society. Storey Publishing. ISBN 978-1-60342-695-4
Native bees, conservation. B. Moisset
You can help pollinators in your own garden. B. Moisset
Bee families, description, classification
Everything About Bees. Everythingabout.net
Native bees biology. The Xerces Society
Native Bees that Pollinate Wild Blueberries. (Families that pollinate blueberries; nests, etc.) Department of Agriculture and Aquaculture of Canada. New Brunswick
The Great Sunflower Project. (Information on bee families).
Understanding Native Bees, the Great Pollinators. University of Maine Cooperative Extension. Bulletin #7153
My thanks to Lorraine Anton for editorial assistance.
Non-native honey bee, Apis mellifera: 1. Queen surrounded by attendants. 2. Swarm. 3. Combs of a feral colony
The honey bee, remarkable as it is, doesn’t know how to pollinate a tomato or an eggplant flower, while some native bees are masters at this. The same thing happens with a number of native plants, such as pumpkins and watermelons, blueberries and cranberries, which are more efficiently pollinated by native bees than by honey bees. Let us take a closer look at this forgotten treasure of native bees.
Native bees come in a wide range of sizes; they are also varied in their shapes, life styles, places they frequent, nests they build, flowers they visit and season of activity. They remain unnoticed by most of us and yet they provide valuable services to all kinds of flowering plants, from wild flowers to some important crops. For instance, the Southeastern blueberry bee is a hard working little creature, capable of visiting as many as 50,000 blueberry flowers in her short life and pollinating enough of them to produce more than 6,000 ripe blueberries worth about $20 at the market. Not every bee that you see flitting about may be worth $20 but all of them combined keep the world of flowering plants going; flowering plants are a key component of most land ecosystems.
Bees are descended from wasps. Most wasps are carnivores; they either prey upon or parasitize other little creatures, mostly other insects, and use this rich protein source to feed their babies. Many millions of years ago, when the first flowering plants begun to bloom, some wasps made a switch from hunting prey to gathering pollen for their brood. Perhaps they were hunting for insects that visited flowers and ate some of the pollen along with their prey. It didn’t take much to find the advantages of consuming pollen over hunting. Pollen is also rich in proteins and doesn’t fight back so it is easy to imagine why they were happy to become vegetarians. Gathering pollen and nectar requires certain adaptations different from those of hunters; so they started to change to meet these requirements and consequently became bees.
Most bees have very furry bodies and the hairs are feathery, better for trapping loose pollen. If you observe bees or bumble bees visiting flowers you will notice that some are totally covered by pollen grains.
1. Pollen covered Diadasia. 2. Plumose hairs (trapping pollen grains)
However, this would not be a very convenient way for transporting their cargo back to the nest, so most have pollen baskets of one sort or another, either on their hind legs or under their bellies. They frequently brush themselves, picking all those loose pollen grains and transferring them to their pollen baskets. They have a fairly long tongue to sip the nectar usually buried in the heart of the flower, and a large crop or a second stomach for carrying it. A few less visible adaptations took place also when bees were evolving from wasps, including a knack for finding flowers through smell, colors and patterns and a good memory to keep going back to the same flowers that yield a good recompense.
1. Tibial scopae of Agapostemon virescens. 2. Abdominal scopa of Megachile centuncularis. 3. Corbiculae of Bombus impatiens
The mother bee uses some of the nectar to mix it with the pollen. She also uses it for her own nutrition; nectar is a high octane fuel and with all the flying she does she needs a lot of fuel. In this respect bees resemble many of their relatives, the wasps.
All bee families have species that take care of their young by building nests and providing food for them. But several families, such as Apidae, Halictidae and Megachilidae have some black sheep, some selfish species that take advantage of their relatives. They have become “cuckoos”, just like there are cuckoos among birds. As with cuckoo birds they lay their eggs in the nests of others. Their babies feed on the stored food and also on the larvae of the unfortunate hosts. Cuckoo bees don’t need to gather pollen and have lost their pollen baskets and much of their hair, in fact, at first sight some of them are often mistaken for wasps.
Aside from cuckoo bees, all bees build nests, stocking them with a nutritious mixture of pollen, nectar and saliva before laying their eggs, and usually sealing them so the babies remain safe. They generally mix the dry pollen with some nectar kneading it into a bee loaf, used to feed their children. They add their own saliva to this mixture. The saliva seems to be an important ingredient that confers some protection against bacteria and fungus infections.
Some build their nests underground, others use hollow stems or holes in trees, perhaps left by beetles, others use their powerful jaws to make holes in wood. Be as it may they start the job of nest building by carefully choosing the best real estate; if conditions aren’t right they continue their search. It wouldn’t do to have their homes flooded or lacking enough sunshine, or being too large or too small for their needs.
Miners
Many members of the larger families, Apidae, Andrenidae, Halictidae, Megachilidae and Colletidae are ground nesters. They choose a bare spot, with sunshine and not likely to get flooded, and start the task of digging that may take several days. They build a long tunnel slightly wider than their own bodies. Some don’t want any neighbors around; on the other hand, others prefer the company of their own sisters. They may make little towns or even large towns; but they still remain solitary in the sense that each digs her own nest and takes care of her own brood all by herself. Still others show different levels of cooperation, sharing the tasks of nest building and food provisioning. This tunnel can be a foot long or even longer. It may twist halfway or take a turn near the end. At the end of the tunnel the mother bee builds a chamber a little wider; this will be the nursery for just one baby. She fills it up with enough food for one bee to grow from egg to full size. There she lays an egg and seals the chamber. She will add other branches to the tunnel; at the end of each there will be another cell or chamber properly stocked and with an egg. Imagine a bunch of grapes; that is what some of those nests look like.
1. Colletes inaequalis at the entrance of its nest. 2. Part of an aggregation of Lasioglossum zephyrum nests. 3. Semisocial Agapostemon virescens sharing the entrance to their nest. 4. Aggregation of Anthophora bomboides nests. 5. Andrena
Hole nesters: masons and leafcutters
Members of several families take advantage of already existing holes; that is, they use hollow stems or holes made by beetles or other agents in trees. There, they construct chambers, usually lined up in a row, which they stock one by one to serve as nurseries.
Most members of the family Megachilidae are hole nesters who use certain materials to prepare the nest properly. Some use clay to build walls between cells and to seal the entrance; therefore they are called mason bees. Others cut round pieces of leaves for the same purpose and also to line the inner walls of the tube; they go by the name of leafcutters. You may have seen those nearly perfect circles missing from the leaves of your rose bushes. Please, don’t begrudge this housing material to such hard working mothers.
1. Megachile albitarsis gathering material for her nest. 2. Young male Osmia cornifrons emerging from nest. 3. Interior of a Megachile xylocopoides’ nest. 4. Megachile sp. sealing nest hole
Carpenters
Other bees use holes of their own making; they have powerful jaws with which they can excavate tunnels in wood. Fortunately they prefer soft wood and dislike paint or other finishing materials; so it is possible to prevent them from doing serious damage to wood structures by taking simple precautions, such as painting or coating any exposed wood. They are called carpenter bees and very likely you have seen some of them and some of their handiwork. There is usually a pile of sawdust below the entrance to the nest.
1. Xylocopa’s nest entrances. 2. Xylocopa virginica at nest’s entrance
Foraging
Some bees are generalists and can use the pollen from a large variety of flowers; but most of them have some degree of specialization and resort to pollen from only a few or even just one kind of flower. However, they may collect nectar from a wider range of flowers in addition to the ones they visit for pollen.
Bombus ternarius visiting different flowers through the seasons
One example of specialization is the squash bee, which is very proficient at visiting flowers of vine crops. A few other examples are blueberry bees, azalea bees, globe mallows bees, which specialize in the mentioned flowers. Some species are active only for a few weeks in the spring and therefore can only use the flowers that are in bloom at that particular time. But others, such as bumble bees, have long lived colonies that start in the spring and last until the fall so they have to keep switching flowers as blooms come and go.
1. Peponapis pruinosa visiting a squash blossom. 2. Habropoda laboriosa on blueberry blossom
Most flowers open their blossoms during the day and produce more nectar and perfume during those hours, so it is not surprising that most species of bees keep the same schedule. However there are a few species in each of the main families of bees that become active only at dawn or dusk; naturally they pollinate those flowers that bloom at such times. They are called crepuscular bees.
In general, when not working, the females rest inside their nests. The males, on the other hand, have nothing to do with nest building or provisioning, so they find other places to rest. Occasionally it is possible to find a cluster of males, clinging by their jaws to flowers or twigs. Squash bee males are frequently found in groups inside the squash blossoms which are beginning to wilt.
1. Cluster of sleeping male Bombus insularis. 2. Male melittid bees, Hesperapis, inside a blossom. 3. Squash bees, Peponapis, in squash blossom. 4. Male Halictus parallelus
The long tongued bees, Apidae and Megachilidae, favor flowers with a longer throat, although they are not averse to sipping nectar from flat open flowers. The remaining families, the short tongued ones, are more limited in their choices and can only take advantage of flowers with easily accessible pollen and nectar.
Long tongues of: 1.Osmia cornifrons. 2. Anthophora abrupta
Families of bees
There are about four thousand different species of bees in North America. The members of the five most common families, Apidae, Halictidae, Andrenidae, Megachilidae and Colletidae can be found throughout the continent from Canada and Alaska to warm and sunny Florida; from forests to deserts; from remote areas to gardens and backyards; even the National Mall in the very heart of our nation’s capital sports a fauna of native bees. Perhaps the only places where bees are absent are the high mountains.
There is even a hardy little soul, the boreal bumble bee, which lives within the Arctic Circle. The young queen starts raising her family when there is still frost on the ground and sometimes she has to spend hours covering her babies to keep them warm. Just like some birds that have a brood patch on their bellies, these bumble bees also have a bare spot to transfer heat from their bodies to their children. Bumble bees and a few other insects are warm blooded animals; they can be real powerhouses that produce energy by vibrating their flight muscles repeatedly. Thus the mother spends long hours shivering to generate the needed heat; this intense effort requires a lot of fuel so she needs to keep sipping honey, an excellent energy source. Finally, after spending long hours taking care of her family, when the sun heats the land, that tired working mother has to leave the nest in search for supplies for the family.
Apidae
This large family includes a wide variety of species, starting with that non-native, the honey bee, Apis mellifera; in fact the name of the family comes from the Latin name for the honey bee, Apis. It includes all the bumble bees, the carpenter bees, several kinds of miner bees and some types of cuckoo bees.
Honey bee: 1. Worker. 2. Comb with some larvae
There are about fifty species of North American bumble bees. Most people are familiar with them; they are big and furry, mostly black with stripes of yellow or white or even bright orange. They have some things in common with honey bees; they are more social than most other bees forming colonies with one queen and many workers, although such colonies are never as big or as long lived as those of honey bees.
1. Bombus affinis. 2. Bombus impatiens. 3. Bombus perplexus. 4. Bombus vosnesenskii. 5. Bombus fervidus
Bumble bees are ground nesters, most make their nests in a cavity; but a few merely build their nests above ground somewhat covered by thatch and debris. The cavities they need for their nests are larger than those of solitary bees, so the first thing that a young queen does in the spring is to find an abandoned mouse nest or a similar burrow. Then it starts insulating it and preparing it for her brood. She builds a few wax pots that she fills up with honey and a larger one which she stocks with a mixture of pollen and nectar and where she lays her eggs, no more than half a dozen at first. They are all sterile female workers; when that batch is fully grown the queen doesn’t abandon the nest again, spending all her time laying more eggs while the workers take care of all the chores in and out of the home. The colony grows rapidly and it can reach as many as a couple of hundred workers although it rarely gets that large. The workers are usually smaller than the queen; that is why you seldom see large bumble bees after the spring. Near the end of the summer the queen lays some male eggs in addition to female ones. The females born at this time become queens, not sterile workers, and they mate soon after they emerge as adults.
All the workers and drones and the old queen die at the end of summer; the only survivors are the new queens, already mated. They find a secluded and safe place to spend the winter and go to sleep; they will start a new colony the next spring.
1. Bombus bimaculatus colony. 2. Bombus impatiens colony
Another thing that bumble bees have in common with honey bees is the kind of pollen baskets, called corbiculae (singular,corbicula), on their hind legs; they are more specialized than the pollen brushes or baskets of other bees which are called scopae (singular, scopa). In honey bees and bumble bees the tibia segment of the hind leg is flattened and has rows of long strong hairs or bristles along the edges of these flattened parts. Thus the shape of these baskets allows them to pack the pollen, mixed with some nectar and saliva into a tight ball rather than the loose mass of pollen grains clinging to the hairs of the scopa of other kinds of bees. A few species of bumble bees have become cuckoos laying their eggs in the nests of other bumble bees. They have no need for workers or for pollen baskets.
Cuckoo bumble bees: 1. Bombus fernaldae. 2. Bombus citrinus
Bumble bees are so good at pollinating tomatoes that their services are put to good use in large green houses that grow tomatoes year round. All that is needed is a queen, a box for the nest and a supply of sugary water because tomatoes produce a lot of pollen but no nectar. The bumble bees are free to come and go but remain content inside the green house most of the time doing their job.
Carpenter bees are also black and large and you may have trouble telling them apart from bumble bees except for one distinctive feature: bumble bees are fuzzy all over, while the abdomen of carpenter bees is almost hairless so it looks rather glossy. Male carpenter bees of some species have a large white patch on their faces. Early in the spring the males establish territories that they patrol and protect zealously not letting other males come near; in fact often they chase away almost anything that moves including unwary gardeners. Sometimes they choose territories near promising nesting sites not because they plan to set housekeeping but because they know that such places will attract females. Fortunately they can’t sting, only females do that, so there is not much to fear and you can let them be. The females have powerful jaws and can dig holes in soft wood to make their nests, hence their name of carpenter.
1. Male Xylocopa virginica patrolling its territory in early spring. 2. Female X. virginica. 3. Female X. virginica sealing the nest entrance
Carpenter bees are not always well behaved pollinators. Occasionally, when a flower has a long throat that places the nectar out of reach, the bee uses her sharp tongue to make a slash at the base of the flower where the nectar is stored. She then drinks it without coming near the pollen dispensing anthers and stigma of the flower. Thus, carpenter bees can be nectar robbers who cheat the flower instead of doing it a service in return for its nectar. Bumble bees and honey bees are also quite capable of this kind of thievery. Look at the trumpet honeysuckles, horse mints or abelias in your garden and you may find the tell tale signs of these attacks.
There are some small relatives of the carpenter bees called small carpenter bees, genus Ceratina, although you would never mistake one for the other because of the size difference. They nest in hollow twigs, or in pithy stems, such as blackberry brambles or roses.
1. Ceratina calcarata. 2. Ceratina arizonensis
One large group within the Apidae family, the Nomadinae, is made exclusively of parasitic bees or cuckoo bees. Nomadinae bees are usually red with whitish markings. They have lost all the adaptations that serve to carry pollen as they don’t need to do so; they are almost hairless and wasp like. Many parasitize the nests of Andrenid bees. They are often seen in early spring flying low, searching for the ground nests of their hosts. When they locate a nest, they wait nearby ready to sneak in and lay an egg while the busy mother, legitimate owner of the nest, goes in search of food. The egg of the cuckoo bee develops rapidly and grows into a larva that will kill and eat the resident baby as well as the food reserves in the nest.
Cuckoo bees: 1. Female Nomada of the luteola subgroup. 2. Female Nomada imbricata inspecting a host’s nest, presumably an andrenid’s. 3. Triepeolus remigatus
Among the miners we can mention some very useful ones such as the squash bee, Peponapis, which pollinates flowers of squash, pumpkin, and other vine crops. They are about the same size and general coloration of a honey bee, but you can easily tell them apart by their behavior when they are near flowers of these crops. They are fine tuned to the daily rhythms of squash flowers so they start their work shift early in the morning when flowers are at their peak. They show no hesitation when approaching a squash flower, plunge right in, briskly collect supplies and leave in a hurry. Honey bees, on the other hand, arrive later at the flowers when they are past their prime; they also take some extra time hovering over the flower and visiting it leisurely. Even with bee hives nearby it is estimated that squash bees do several times more pollination than honey bees. Vine crop growers are very aware of their value as pollinators. These bees usually nest under the very plants they pollinate. If you are one of those who pick up your own pumpkin to make a Jack-o-lantern, you will be walking over some nests full of sleeping young squash bees.
Mating Peponapis pruinosa bees
One spectacular member of this family is a recent arrival from the tropics, the orchid bee, Euglossa, which somehow found its way into Florida; nobody knows how.
Euglossa viridissima: 1. Male with enlarged hind tibiae. 2. Female with corbicula full of pollen
The industrious $20 bee, the blueberry bee, Habropoda laboriosa, mentioned above and many of its relatives, the Anthophorini, belong to this family. They are mostly hairy, heavy set bees with impressively long tongues.
1. Habropoda depressa. 2. Anthophora centriformis
Megachilidae
This family contains the called mason bees and leaf-cutter bees. Most of them nest in holes, either in wood or hollow twigs, but there are also a few that nest in the ground. There are a few species within this family that are not native but have been introduced either intentionally or unintentionally in this country. Among the intentional introductions there is the Japanese bee or horned bee, which is considered an excellent pollinator of fruit trees. One interesting characteristic of the members of this family is that they don’t carry the pollen on their back legs but on their bellies. If you happen to see a bee, about the size of a honey bee, with a yellow belly you can be sure that it is a Megachilid bee.
1. Lithurgus apicalis. 2. Megachile inermis. 3. Cuckoo bee: Coelioxys modesta
The blue orchard bee, Osmia lignaria, and specially the variety Osmia lignaria lignaria of western United States is being developed for pollination of fruit trees by providing nest houses. It may prove to be an excellent replacement for the beleaguered honey bee.
Osmia lignaria
Halictidae
Some of the prettiest bees belong to this family; with their shiny metallic colored bodies they capture your heart. Many are metallic green, but others have shades of color that go from blue to copper or gold. Most of them nest in the ground, some are completely solitary but others share the entrance to their nests. In most cases that is all they share and don’t go to the extent of being truly social. However, a few go a step further and show some division of labor in guarding the entrance to their homes and rearing of the young; they are usually sisters that came from the same nest. Some species go even further in their level of socialization and can be considered truly social, with a division of labor in which the mother and starter of the colony lays eggs and lets the daughters do all the other work.
1. Male Agapostemon splendens. 2. Augochloropsis metallica. 3. Augochlorella sp.
Not all are metallic green; there are some black ones, also. Among these there are some that are solitary while others, such as some in the genus Halictus, are social. They may have from a few to many females sharing family rearing; however, their colonies never reach the complex social structure of those of bumble bees and honey bees.
1. Halictus confusus, nectaring. 2. The social Halictus tripartitus at the nest
One attractive halictid is Augochlora pura (the name means the pure magnificent green bee) found in the eastern United States. She has the peculiar habit of building her nest under the bark of a rotten log. She takes advantage of the loose, half rotten material to make some sort of bedding adding her own saliva and secretions to build an envelope for the larvae and accumulated food. It kneads the pollen into a number of little loaves shaped like tiles, which she plasters on the inner wall of the brood chamber and lays an egg before sealing the cell completely. This precaution is absolutely necessary with all the marauding ants and other hungry creatures that abound under loose bark.
Augochlora pura: 1. Adult females. 2. Nest. 3. Female and larva
A very useful halictid bee is the alkali bee, Nomia melanderi, of western United States. As its name suggests it prefers to build its nest in alkaline terrain. It likes to live in aggregations or colonies, not exactly social since each bee tends to her own brood, but companionably close to each other. It is a very good pollinator of alfalfa and some growers take advantage of its nesting habits to manage this species to some extent. They supply the appropriate terrain for their nesting needs near alfalfa crops even creating it artificially by using tarp, covering it with clay and watering it as needed to create the best conditions.
Nomia melanderi
There are also some cuckoo species in this family and, just like the other cuckoo bees, they are almost hairless and somewhat wasp like. Some have a bright red abdomen.
Cuckoo halictid bee, Sphecodes davisii
Andrenidae
The andrenid bees are all ground nesters. This is a very large family. Many are dark, black, and rather non-descript bees; others have bright red colors. those in the genus Perdita can be quite striking, metallic greenish, or with yellow markings. They can be distinguished from other bees by the velvety areas (fovea) on the face, between the eyes and the base of the antennae. Andrenids are among the earliest bees to emerge in the spring. You can see them visiting violets and other early blooming flowers. Some andrenid bees are very good pollinators of apple blossoms. Many of them are active only during this brief period. The next generation remains sound asleep underground through summer, fall and winter only to emerge the next spring when their favorite flowers are in bloom.
1. Andrena nubecula. 2. Perdita sp. 3. Andrena prunorum. 4. Andrena sp. showing the hairy facial fovea
What would the forests be without azaleas and rhododendrons? Their flowers are the kind that honey bees cannot pollinate. These flowers don’t release their pollen like most flowers, but hold it inside the anthers waiting for some skillful bee that knows how to shake it, just like a saltshaker. Bumblebees and a number of solitary bees are good at this; the Cornell azalea bee (Andrena cornelli) is one of them, a dark colored, slender bee which is found in the eastern United States. It is never too far from azaleas or rhododendrons because their pollen is its favorite food. Besides being very competent at shaking the anthers, her pollen baskets with long widely spaced hairs, are especially adapted to the particular clumpy texture of these flowers’ pollen.
Andrena cornelli
Colletidae
This is a small family sometimes considered as more primitive than other bees because their tongues (glossa) are broad and wasp-like. Some colletids, the yellow-masked bees, such as Hylaeus, don’t even have baskets to carry pollen so they have to carry it inside their crops. They are not as hairy as other bees and can easily be mistaken for wasps. Many are ground nesters; sometimes forming large aggregations. Those in the genus Hylaeus don't dig nests but use available cavities such as hollow twigs. The members of this family use a cellophane-like material to line the chambers where they lay their eggs; so sometimes they are called cellophane bees.
1. Colletes hyalinus. 2. Hylaeus sp. 3. "Cellophane" lined cell of a colletid bee
Melittidae
Finally, there is an even smaller family of bees, the melittid bees, represented by only a few species. Most of them use pollen from just one species or a few species of plants. Some also use floral oils to feed their brood. According to recent DNA studies, this family rather than Colletidae would be the basal branch of bees, or the most primitive.
Hesperapis regularis
Bee mimics
Last but not least, let us mention those superb impersonators of bees, certain flies which are frequent flower visitors, in particularSyrphid or flower flies, bee flies and a few robber flies. Don’t be fooled by them, despite their appearance they are not bees but flies; they don’t have a sting as bees do, so they masquerade as bees to fool hungry birds. Often they succeed at fooling the inexperienced observer of bees, too.
They have only one pair of wings instead of two. This is a very significant difference but nearly impossible to notice when they are flying about. Part of the reason for this difficulty is that bees’ wings have tiny hooks that lock the front and hind wings together making them appear as just one. There are several other differences that would be more helpful to the observer of living flower visitors such as bees and flies. These flower visiting flies have huge eyes, very short antennae and skinny legs when compared to bees.
Syrphid flies: 1. Toxomerus marginatus. 2. Eristalis tenax. 3. Mallota bautias. Beefly: 4. Bombylius major. Robber fly: 5 Laphria thoracica
Additional readings
References in Anthophila, at the bottom of the page.
Goulson, Dave (2003). Bumblebees, Behaviour and Ecology. Oxford University Press, Oxford OS2 6DP ISBN 978-0-19-852607-0
O'Toole, Christopher, Raw, Anthony (1999). Bees of the world. Cassell Illustrated. ISBN 0-8160-5712-5
Mader, E., Shepherd, M., Vaughan, M., Black, S. H., LeBuhn, G. (2011). Attracting Native Pollinators. The Xerces Society. Storey Publishing. ISBN 978-1-60342-695-4
Native bees, conservation. B. Moisset
You can help pollinators in your own garden. B. Moisset
Bee families, description, classification
Everything About Bees. Everythingabout.net
Native bees biology. The Xerces Society
Native Bees that Pollinate Wild Blueberries. (Families that pollinate blueberries; nests, etc.) Department of Agriculture and Aquaculture of Canada. New Brunswick
The Great Sunflower Project. (Information on bee families).
Understanding Native Bees, the Great Pollinators. University of Maine Cooperative Extension. Bulletin #7153
My thanks to Lorraine Anton for editorial assistance.
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