Bees
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Bees are flying insects, closely related to wasps and ants. Bees are a monophyletic lineage within the superfamily Apoidea, presently classified by the unranked taxon name Anthophila. There are slightly fewer than 20,000 known species of bee, though many are undescribed and the actual number is probably higher. They are found on every continent except Antarctica.
Introduction
Many species of bees are poorly known. The smallest bee is the dwarf bee (Trigona minima) and it is about 2.1 mm (5/64") long. The largest bee in the world is Megachile pluto, which can be as large as 39 mm (1.5"). The most common type of bee in the Northern Hemisphere are the many species of Halictidae, or sweat bees, though this may come as a surprise to people, as they are small and often mistaken for wasps or flies.
The most well-known bee species is the Western honey bee, which, as its name suggests, produces honey, as do a few other types of bee. Human management of this species is known as beekeeping or apiculture.
Bees are adapted for feeding on nectar and pollen, the former primarily as an energy source, and the latter primarily for protein and other nutrients. Most pollen is used as food for larvae.
Bees have a long proboscis (a complex "tongue") that enables them to obtain the nectar from flowers. Bees have antennae almost universally made up of thirteen segments in males and twelve in females, as is typical for the superfamily. They all have two pairs of wings, the hind pair being the smaller of the two; in a very few species, one sex or caste has relatively short wings that make flight difficult or impossible, but none are wingless.
Pollination
Bees play an important role in pollinating flowering plants, and are the major type of pollinators in ecosystems that contain flowering plants. Bees may focus on gathering nectar or on gathering pollen, depending on their greater need at the time. Bees gathering nectar may accomplish pollination, but bees that are deliberately gathering pollen are more efficient pollinators. It is estimated that one third of the human food supply depends on insect pollination, most of this accomplished by bees.
Most bees are fuzzy and carry an electrostatic charge, thus aiding in the adherence of pollen. Female bees periodically stop foraging and groom themselves to pack the pollen into the scopa, which is on the legs in most bees, and on the ventral abdomen on others, and modified into specialized pollen baskets on the legs of honey bees and their relatives. Many bees are opportunistic foragers, and will gather pollen from a variety of plants, but many others are oligolectic, gathering pollen from only one or a few types of plant. A small number of plants produce nutritious floral oils rather than pollen, which are gathered and used by oligolectic bees. One small subgroup of stingless bees (called "vulture bees") is specialized to feed on carrion, and these are the only bees that do not u se plant products as food. Pollen and nectar are usually combined together to form a "provision mass", which is often soupy, but can be firm. It is formed into various shapes (typically spheroid), and stored in a small chamber (a "cell"), with the egg deposited on the mass. The cell is typically sealed after the egg is laid, and the adult and larva never interact directly (a system called "mass provisioning").
Bees are extremely important as pollinators in agriculture, especially the domesticated Western honey bee, with contract pollination having overtaken the role of honey production for beekeepers in many countries. Monoculture and pollinator decline have increasingly caused honey bee keepers to become migratory so that bees can be concentrated in areas of pollination need at the appropriate season. Many other species of bees are increasingly cultured and used to meet the agricultural pollination need. Bees also play a major, though not always understood, role in providing food for birds and wildlife. Many of these bees survive in refuge in wild areas away from agricultural spraying, only to be poisoned in massive spray programs for mosquitoes, gypsy moths, or other pest insects.
Visiting flowers is a dangerous occupation with high mortality rates. Many assassin bugs and crab spiders hide in flowers to capture unwary bees. Others are lost to birds in flight. Insecticides used on blooming plants can kill large numbers of bees, both by direct poisoning and by contamination of their food supply. A honey bee queen may lay 2000 eggs per day during spring buildup, but she also must lay 1000 to 1500 eggs per day during the foraging season, simply to replace daily casualties.
The population value of bees depends partly on the individual efficiency of the bees, but also on the population itself. Thus, while bumblebees have been found to be about ten times more efficient pollinators on cucurbits, the total efficiency of a colony of honey bees is much greater, due to greater numbers. Likewise, during early spring orchard blossoms, bumblebee populations are limited to only a few queens, thus they are not significant pollinators of early fruit.
Standard Cyclopedia of Horticulture
Read about Bees in the Standard Cyclopedia of Horticulture
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Bees in Horticulture. Bees pollinate the greatest number of flowers of any insects. To them, therefore, horticulturists arc indebted for a service that is inestimable, but it is usually disregarded. The progressive horticulturist, however, today is awake to the situation and ready to utilize the honey-bee in an effort better to meet competition. The bee's service to the horticulturist in pollinating the flowers of fruit s and vegetables, is the result of its effort to secure nectar or pollen, the male element of the flower; this is transplanted from the anther to the stigma, which latter is the female organ. Many flowers, for satisfactory fertilization, require a foreign pollen, and it is through the agency of bees that this is usually supplied. The intricacies of the mechanisms and the means of pollination have been described by a host of writers, including Darwin and Muller. There are two kinds of bees, solitary and colonial (social). Solitary bees live isolated and singly, seldom becoming numerous. Among the colonial bees are the bumblebee and honey-bee. While the honey-bee may be classed as wild when colonies escape from apiaries, wild bees may be considered to include all bees other than the honey bee. While wild bees are sometimes numerous and may be observed at work on the apple, raspberry and many other flowers, the honey-bee in most localities, probably outnumbers them. If it were possible to calculate the value derived from pollination by the honey-bee alone, these returns without doubt far exceed the total income of beekeepers through their honey and wax. In the bee, therefore, there is a source of double income. Among the cultivated plants in northern latitudes that are pollinated by bees, are the apple, pear, plum, quince, peach, raspberry, blackberry and strawberry (to some extent), mulberry, pea, bean, currant, grape, squash, melon, cucumber and the cranberry. The value of the honey-bee in the cultivation of the cranberry was but recently recognized and is mentioned on next page. While growers of fruits and vegetables have usually recognized that bees play an important part in their croppage, they have largely depended on the wild bees or bees in neighboring apiaries for service. There is, however, some risk in this, because the seasons vary and the prevalence of insect- and bee-life varies from year to year. It is well known that the prevalence of all wild life, plant or animal, is subject to fluctuations due to favorable and unfavorable environmental conditions. Some years in a locality there is a pest of mosquitos or house- flies. In succeeding years they may be few. It is so with the game birds and the fish of the sea; they are plenty or scarce from time to time. Bees also have their periods of ups and downs. When favored, they rise to the crest of prosperity and prevalence. It may be that disease enters a locality and reduces their numbers. Hard winters may also depreciate them so that in a year when they are needed for their service as pollen- bearers, they are at a low ebb. Fig. 498 illustrates the hypothetical curve of this fluctuation. When the horticulturist realizes that he is depending on this fluctuating service of wild bees, he asks what he can do to overcome the unreliability and assure himself of a maximum crop or a more even crop. The recommendation would be to establish an apiary in proportion to the size of the orchard or garden. This eliminates any dependency upon wild bees or honeybees from neighboring apiaries. Yet their additional service will do no harm. It is far better to over-supply an orchard with bees during the blooming period than to have a scarcity. Furthermore, the cost of the small apiary is infinitesimal as compared with the possible benefits and returns. It should also be remembered that during fruit- bloom particularly, weather conditions often prohibit free flight of bees. Hence they should be near at hand to perform their service. Numerous observations are on record in which orchards were successfully fertilized when the bees had less than a quarter of a mile to fly, while more distant orchards bore no crops. Thus the apiary in or adjacent to an orchard will safeguard failure. A specific instance of the importance of bees to the practical orchardist, is shown in an observation on two orchards of about equal acreage in a western "pocket" in the foothills of an admirable fruit land, well drained and protected from frost. One grower secured large crops, while his neighbor secured none, although his fruit trees were of the same age and blossomed heavily each spring. The owner, in despair of financial ruin, called for assistance upon the State Experiment Station. A specialist, who was a pomologist and entomologist, investigated the two entirely comparable orchards, but was about to return without solving the problem when the question of bees arose. Upon inquiry it was asserted that no bees had been maintained for either orchard. Going over the ground more carefully, however, the specialist found m a neglected corner of the fruiting orchard, a fallen log partially sunken in the damp land. This sheltered a very large colony of bees; to it is attributed the success of the orchard. The following season bees were provided in the orchard which had previously failed, with the result that the owner netted $3,800 on his crop. Special services of bees. Various fruits.—The honey-bee has been known to work the strawberry although it does not always frequent it. There is, however, a particular affinity in the raspberry for bees. One of the sources of the finest honey is the wild raspberry- The blackberry is less frequently visited. Plums benefit materially. Cranberry.—Recently investigations have shown the bees to be of prime importance in the setting of cranberries. In cranberry-growing in Massachusetts, owners are maintaining their own apiaries. It may be desirable to have one colony for every two acres. The growers of melons use colonies of bees on their plantations with most marked success. Similarly, cucumber- growers for pickling-houses and squash-growers regularly maintain bees. General market-gardeners also believe in the benefits derived. Apple and peach orchards.—Apple and pear crops as well as peach and plum are, without doubt, more even, larger and more constant when bees are kept. In Vermont it has recently been noticed that the largest apple crops occur in the vicinity of the commercial apiaries. It is fast becoming the custom among commercial growers to maintain their own apiaries adjacent to or in their orchards. Some advocate a colony of bees for every fifty trees. In greenhouses.—For the fertilization of vegetables and fruits in greenhouses, bees are of material service, haying largely done away with the use of the camel's- hair brush, impossible for commercial growers. For example, in Massachusetts, one grower of greenhouse cucumbers uses upwards of eighty colonies a year. The total number used annually in the state by greenhouse cucumber-growers exceeds 2,000 colonies. It is believed by some that tomatoes in the greenhouse benefit to some extent by the service of bees. The alleged injury to fruit by bees. Occasionally it is alleged that bees damage an orchard. It might be concluded when bees are seen upon peaches, grapes or pears, sucking at the flesh, that the bee is injurious. On the other hand if this act could have been traced, it would have been found that something other than a bee had first pierced the skin of the fruit. Investigation shows that wasps and birds do this, or that a fungus may disintegrate the skin. In some such break in the skin the honey-bee can make a start; but to the satisfaction of all beekeepers and most orchardists, it has been proved by experiments and demonstrations that the honey-bee is physically incapable of puncturing a sound fruit. Thus, the injury by bees to fruit is a misconception; the news should be spread by successful orchardists. Securing of bees. Bees are available to horticulturists in several ways. A small number of colonies is sometimes hired for a period of a few weeks, during the blossoming period of the crop. Growers occasionally induce beekeepers to establish an apiary in their orchards by granting them privileges. Bee-keepers sometimes approach orchardists for the location of the apiary. The more thoughtful grower, however, considers it advisable to own his bees. These he maintains himself or hires kept by a practical apiarist. The practice is growing in favor, especially among moderate-sized orchardists or cranberry-growers, of hiring a practical apiarist to maintain the colonies on several adjacent farms. This cooperative plan insures a maximum efficiency of the colonies at a minimum cost and without burdening the horticulturist with additional detail. Those who use bees in greenhouses will find it advantageous to maintain colonies rather than to purchase annually. In buying bees it is particularly essential to secure disease-free stock. Bees are subject to at least two prevalent diseases, known as "American foul brood" and "European foul brood," to which they succumb rapidly. The inexperienced, therefore, should secure information and ascertain that the bees have been inspected for disease, when this is possible. Should disease set in, a considerable loss, both in bees and to the orchard, might result in a short time. Information concerning diseases can usually be had through the experiment stations or agricultural colleges as well as the United States Department of Agriculture. Manipulation of bees. There are numerous books and bulletins upon the manipulation of colonies. A few fundamental features are: Always keep the colonies strong; secure an amiable race so that the bees may be handled agreeably; keep the colonies in hives from which the combs may be removed; eliminate swarming; give adequate protection in winter; feed when necessary. If the inexperienced grower is to manipulate his own bees, it is advised that he begin with a small number of colonies, say not more than five. If the bee-moth becomes prevalent in the hive, it is a sign that something is radically wrong with the colony. An experienced apiary inspector always suspects the presence of disease when moths are found.
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Eusocial and semisocial bees
Bees may be solitary or may live in various types of communities. The most advanced of these are eusocial colonies found among the honey bees, bumblebees, and stingless bees. Sociality, of several different types, is believed to have evolved separately many times within the bees.
In some species, groups of cohabiting females may be sisters, and if there is a division of labor within the group, then they are considered semisocial.
If, in addition to a division of labor, the group consists of a mother and her daughters, then the group is called eusocial. The mother is considered the "queen" and the daughters are "workers". These castes may be purely behavioral alternatives, in which case the system is considered "primitively eusocial" (similar to many paper wasps), and if the castes are morphologically discrete, then the system is "highly eusocial".
There are many more species of primitively eusocial bees than highly eusocial bees, but they have been rarely studied. The biology of most such species is almost completely unknown. The vast majority are in the family Halictidae, or "sweat bees". Colonies are typically small, with a dozen or fewer workers, on average. The only physical difference between queens and workers is average size, if they differ at all. Most species have a single season colony cycle, even in the tropics, and only mated females (future queens, or "gynes") hibernate (called diapause). A few species have long active seasons and attain colony sizes in the hundreds. The orchid bees include a number of primitively eusocial species with similar biology. Certain species of allodapine bees (relatives of carpenter bees) also have primitively eusocial colonies, with unusual levels of interaction between the adult bees and the developing brood. This is "progressive provisioning"; a larva's food is supplied gradually as it develops. This system is also seen in honey bees and some bumblebees.
Highly eusocial bees live in colonies. Each colony has a single queen, together with workers and, at certain stages in the colony cycle, drones. When humans provide a home for a colony, the structure is called a hive. A honey bee hive can contain up to 40,000 bees at their annual peak, which occurs in the spring, but usually have fewer.
Bumblebees
- Main article: Bumblebee
Bumblebees (Bombus terrestris, B. pratorum, et al.) are eusocial in a manner quite similar to the eusocial Vespidae such as hornets. The queen initiates a nest on her own (unlike queens of honey bees and stingless bees which start nests via swarms in the company of a large worker force). Bumblebee colonies typically have from 50 to 200 bees at peak population, which occurs in mid to late summer. Nest architecture is simple, limited by the size of the nest cavity (pre-existing), and colonies are rarely perennial. Bumblebee queens sometimes seek winter safety in honey bee hives, where they are sometimes found dead in the spring by beekeepers, presumably stung to death by the honey bees. It is unknown whether any survive winter in such an environment.
Stingless bees
- Main article: Stingless bee
Stingless bees are very diverse in behavior, but all are highly eusocial. They practice mass provisioning, complex nest architecture, and perennial colonies.
Honey bees
- Main article: Honey bee
The true honey bees (genus Apis) have arguably the most complex social behavior am ong the bees. The Western (or European) honey bee, Apis mellifera, is the best known bee species and one of the best known of all insects.
Africanized honey bee
- Main article: Africanized bee
Africanized bees, also called killer bees, are a hybrid strain of Apis mellifera derived from experiments to cross European and African honey bees by Warwick Estevam Kerr. Several queen bees escaped his laboratory in South America and have spread throughout the Americas. Africanized honey bees are more defensive than European honey bees.
Solitary and communal bees
Most other bees, including familiar species of bee such as the Eastern carpenter bee (Xylocopa virginica), alfalfa leafcutter bee (Megachile rotundata), orchard mason bee (Osmia lignaria) and the hornfaced bee (Osmia cornifrons) are solitary in the sense that every female is fertile, and typically inhabits a nest she constructs herself. There are no worker bees for these species. Solitary bees typically produce neither honey nor beeswax. They are immune from acarine and Varroa mites (see diseases of the honey bee), but have their own unique parasites, pests and diseases.
Solitary bees are important pollinators, and pollen is gathered for provisioning the nest with food for their brood. Often it is mixed with nectar to form a paste-like consistency. Some solitary bees have very advanced types of pollen carrying structures on their bodies. A very few species of solitary bees are being increasingly cultured for commercial pollination.
Solitary bees are often oligoleges, in that they only gather pollen from one or a few species/genera of plants (unlike honey bees and bumblebees which are generalists). No known bees are nectar specialists; many oligolectic bees will visit multiple plants for nectar, but there are no bees which visit only one plant for nectar while also gathering pollen from many different sources. Specialist pollinators also include bee species that gather floral oils instead of pollen, and male orchid bees, which gather aromatic compounds from orchids (one of the only cases where male bees are effective pollinators). In a very few cases only one species of bee can effectively pollinate a plant species, and some plants are endangered at least in part because their pollinator is dying off. There is, however, a pronounced tendency for oligolectic bees to be associated with common, widespread plants which are visited by multiple pollinators (e.g., there are some 40 oligoleges associated with creosotebush in the US desert southwest[1], and a similar pattern is seen in sunflowers, asters, mesquite, etc.)
Solitary bees create nests in hollow reeds or twigs, holes in wood, or, most commonly, in tunnels in the ground. The female typically creates a compartment (a "cell") with an egg and some provisions for the resulting larva, then seals it off. A nest may consist of numerous cells. When the nest is in wood, usually the last (those closer to the entrance) contain eggs that will become males. The adult does not provide care for the brood once the egg is laid, and usually dies after making one or more nests. The males typically emerge first and are ready for mating when the females emerge. Providing nest boxes for solitary bees is increasingly popular for gardeners. Solitary bees are either stingless or very unlikely to sting (only in self defense, if ever).
While solitary females each make individual nests, some species are gregarious, preferring to make nests near others of the same species, giving the appearance to the casual observer that they are social. Large groups of solitary bee nes ts are called aggregations, to distinguish them from colonies.
In some species, multiple females share a common nest, but each makes and provisions her own cells independently. This type of group is called "communal" and is not uncommon. The primary advantage appears to be that a nest entrance is easier to defend from predators and parasites when there are multiple females using that same entrance on a regular basis.
Cleptoparasitic bees
Cleptoparasitic bees, commonly called "cuckoo bees" because their behavior is similar to cuckoo birds, occur in several bee families, though the name is technically best applied to the apid subfamily Nomadinae. Females of these bees lack pollen collecting structures (the scopa) and do not construct their own nests. They typically enter the nests of pollen collecting species, and lay their eggs in cells provisioned by the host bee. When the cuckoo bee larva hatches it consumes the host larva's pollen ball, and if the female cleptoparasite has not already done so, kills and eats the host larva. In a few cases where the hosts are social species, the cleptoparasite remains in the host nest and lays many eggs, sometimes even killing the host queen and replacing her.
Many cleptoparasitic bees are closely related to, and resemble their hosts in looks and size, (i.e., the Bombus subgenus Psithyrus, which are parasitic bumble bees that infiltrate nests of species in other subgenera of Bombus). This common pattern gave rise to the ecological principle known as "Emery's Rule". Others parasitize bees in different families, like Townsendiella, a nomadine apid, one species of which is a cleptoparasite of the melittid genus Hesperapis, while the other species in the same genus attack halictid bees.
"Nocturnal" bees
Four bee families (Andrenidae, Colletidae, Halictidae, and Apidae) contain some species that are crepuscular (these may be either the "vespertine" or "matinal" type). These bees have greatly enlarged ocelli, which are extremely sensitive to light and dark, though incapable of forming images. Many are pollinators of flowers that themselves are crepuscular, such as evening primroses, and some live in desert habitats where daytime temperatures are extremely high.
Miscellaneous
Bees figure prominently in mythology. See Bee (mythology).
Bees are the favorite meal of Merops apiaster, a bird. Other common predators are kingbirds, mockingbirds, bee wolves, and dragonflies.
Yellowjackets and hornets, especially when encountered as flying pests, are often mischaracterized as "bees".
Bees are often affected or even harmed by encounters with toxic chemicals in the environment (for example, see Bees and toxic chemicals).
Despite the bee's painful sting and the typical attitude towards insects as pests, people generally hold bees in high regard. This is most likely due to their usefulness as pollinators and as producers of honey, their social nature, and their diligence. Although a honey bee sting can be deadly to some, bee species are generally non-aggressive if undisturbed, and many cannot sting at all. Bees are used to advertise many products, particularly honey and foods made with honey, thus being one of the few insects used on advertisements.
Gallery
Western honey bee. Brisbane, Australia
Western honey bee on a Sphaeralcea flower. Mesa, Az
Western honey bee in a Sphaeralcea flower. Mesa, Az
Sweat bee, Agapostemon virescens (female) on a Coreopsis flower. Madison, Wi
Bumblebee, Bombus sp. startles Agapostemon virescens. Madison, Wi
Bumblebee,
Bee on lavender
See also
References
- Grimaldi, D. and Engel, M.S. (2005). Evolution of the Insects. Cambridge University Press. ISBN 0-521-82149-5.
- The Bees of the World, C. D. Michener (2000)
- Monographia Apum Angliae, William Kirby (1802)
External links
- All Living Things Images, identification guides, and maps of bees
- Bee Genera of the World
- Bees, Wasps and Ants Recording Society (UK)
- Carl Hayden Bee Research Center
- Rescuing Australian stingless bees
- The first bee of spring
- Solitary Bees & Things Solitary Bees in British gardens
- Search for North American species at Bugguide here
- Bee images on Morphbank, biological image database
