The
Western honey bee or European honey bee (Apis mellifera) is a species
of honey bee. The genus Apis is Latin for "bee", and mellifera
comes from Latin melli- "honey" and ferre "to bear"hence
the scientific name means "honey-bearing bee". The name
was coined in 1758 by Carolus Linnaeus who, realizing that the bees
do not bear honey, but nectar, tried later to correct it to Apis
mellifica ("honey-making bee") in a subsequent publication.
However, according to the rules of synonymy in zoological nomenclature,
the older name has precedence. As of October 28, 2006, the Honey
Bee Genome Sequencing Consortium fully sequenced and analyzed the
genome of Apis mellifera.
In
2007 media attention focused on colony collapse disorder, a decline
in European honey bee colonies in a minority of regions of North
America.
Geographic Distribution
The honey bee is native to the continents of Europe, Asia, and Africa.
As of the early 1600s, the insect was introduced to North America,
with subsequent introductions of other European subspecies two centuries
later.[1] Since then, they have spread throughout the Americas.
Biology,
Life Cycle
In the temperate zone, honey bees survive winter as a colony, and
the queen begins egg laying in mid to late winter, to prepare for
spring. This is most likely triggered by longer day length. She
is the only fertile female, and deposits all the eggs from which
the other bees are produced. Except for a brief mating period when
she may make several flights to mate with drones, or if she leaves
in later life with a swarm to establish a new colony, the queen
rarely leaves the hive after the larvae have become full grown bees.
The queen deposits each egg in a cell prepared by the worker bees.
The egg hatches into a small larva which is fed by nurse bees (worker
bees who maintain the interior of the colony). After about a week,
the larva is sealed up in its cell by the nurse bees and begins
the pupal stage. After another week, it will emerge an adult bee.
For the first ten days of their lives, the female worker bees clean
the hive and feed the larvae. After this, they begin building comb
cells. On days 16 through 20, a worker receives nectar and pollen
from older workers and stores it. After the 20th day, a worker leaves
the hive and spends the remainder of its life as a forager. The
population of a healthy hive in mid-summer can average between 40,000
and 80,000 bees.
The
larvae and pupae in a frame of honeycomb are referred to as frames
of brood and are often sold (with adhering bees) by beekeepers to
other beekeepers to start new beehives.
Both
workers and queens are fed "royal jelly" during the first
three days of the larval stage. Then workers are switched to a diet
of pollen and nectar or diluted honey, while those intended for
queens will continue to receive royal jelly. This causes the larva
to develop to the pupa stage more quickly, while being also larger
and fully developed sexually. Queen breeders consider good nutrition
during the larval stage to be of critical importance to the quality
of the queens raised, good genetics and sufficient number of matings
also being factors. During the larval and pupal stages, various
parasites can attack the pupa/larva and destroy or damage it.
Queens are not raised in the typical horizontal brood cells of the
honeycomb. The typical queen cell is specially constructed to be
much larger, and has a vertical orientation. However, should the
workers sense that the old queen is weakening, they will produce
emergency cells known as supersedure cells. These cells are made
from a cell with an egg or very young larva. These cells protrude
from the comb. As the queen finishes her larval feeding, and pupates,
she moves into a head downward position, from which she will later
chew her way out of the cell. At pupation the workers cap or seal
the cell. Just prior to emerging from their cells, young queens
can often be heard "piping". The purpose of this sound
is not yet fully understood.
Worker
bees are infertile females, but in some circumstances, generally
only in times of severe stress or with the loss or injury or declining
health of the queen, they may lay infertile eggs, and in some subspecies
these eggs may actually be fertile. However, since the worker bees
are 'imperfect' females (not fully sexually developed), they do
not mate with drones. Any fertile eggs that they lay would be haploid,
having only the genetic contribution of their mother, and in honey
bees these haploid eggs will always develop into drones. Worker
bees also secrete the wax used to build the hive, clean and maintain
the hive, raise the young, guard the hive and forage for nectar
and pollen.
In honey bees, the worker bees have a modified ovipositor called
a stinger with which they can sting to defend the hive, but unlike
other bees of any other genus (and even unlike the queens of their
own species), the stinger is barbed. Contrary to popular belief,
the bee will not always die soon after stinging: this is a misconception
based on the fact that a bee will usually die after stinging a human
or other mammal. The sting and associated venom sac are modified
so as to pull free of the body once lodged (autotomy), and the sting
apparatus has its own musculature and ganglion which allow it to
keep delivering venom once detached. It is presumed that this complex
apparatus, including the barbs on the sting, evolved specifically
in response to predation by vertebrates, as the barbs do not function
(and the sting apparatus does not detach) unless the sting is embedded
in elastic material. Even then, the barbs do not always "catch",
so a bee may occasionally pull the sting free and either fly off
unharmed, or sting again.
Drones
Drone bees are the male bees of the colony. Since they do not have
ovipositors, they also do not have stingers. Drone honey bees do
not forage for nectar or pollen. In some species, drones are suspected
of playing a contributing role in the temperature regulation of
the hive. The primary purpose of a drone bee is to fertilize a new
queen. Multiple drones will mate with any given queen in flight,
and each drone will die immediately after mating; the process of
insemination requires a lethally convulsive effort. Drone honey
bees are haploid (having single, unpaired chromosomes) in their
genetic structure and are descended only from their mother, the
queen. They truly do not have a father. In essence, drones are the
equivalent of flying gametes. In regions of temperate climate, the
drones are generally expelled from the hive before winter and left
to die of cold and starvation, since they are unable to forage or
produce honey or take care of themselves.
Life
Expectancy
The average lifespan of the queen in most subspecies is three to
four years. However, there are reports that in the German/European
Black Bee subspecies that was previously used for beekeeping, the
queen was said to live up to 8 years. Because queens deplete their
store of sperm, towards the end of their life they start laying
more and more unfertilized eggs. Beekeepers therefore frequently
change queens every year or every other year.
The
lifespan of the workers varies drastically over the year in places
with an extended winter. Workers born in the spring and summer will
work hard and live only a few weeks, whereas those born in the autumn
will stay inside for several months as the colony clusters. On average
during the year about one percent of a colony's worker bees die
naturally per day. Except for the queen, all of the colony's workers
are therefore exchanged about every four months.
Honey
Production
Bees produce honey by collecting nectar, which is a clear liquid
consisting of nearly 80% water with complex sugars. The collecting
bees store the nectar in a second stomach and return to the hive
where worker bees remove the nectar. The worker bees digest the
raw nectar for about 30 minutes using enzymes to break up the complex
sugars into simpler ones. Raw honey is then spread out in empty
honeycomb cells to dry, which reduces the water content to less
than 20%. When nectar is being processed, honey bees create a draft
through the hive by fanning with their wings. Once dried, the cells
of the honeycomb are sealed (capped) with wax to preserve the honey.
When
a hive detects smoke, many bees become remarkably non-aggressive;
it is speculated that this is a defense mechanism. Wild colonies
generally live in hollow trees, and when bees detect smoke it is
presumed that they prepare to evacuate from a forest fire, carrying
as much food reserve as they can. In order to do this, they will
go to the nearest honey storage cells and gorge on honey. In this
state they are quite docile since defense from predation is less
important than saving as much food as possible.
Thermoregulation
The honey bee needs an internal body temperature of 35 °C (95
°F) to fly which is also the temperature maintained within
the cluster. The same temperature is required in the brood nest
over a long period to develop the brood, and it is the optimal temperature
for the creation of wax. The temperature on the periphery of the
cluster varies with the outside air temperature and in the winter
cluster, the internal temperature may be as low as 2022 °C
(6872 °F).
Honey
bees are able to forage over a 30 °C (54.0 °F) range of
air temperature, largely because they have behavioural and physiological
mechanisms for regulating the temperature of their flight muscles.
From very low to very high air temperatures, the successive mechanisms
are; shivering before flight and stopping flight for additional
shivering, passive body temperature regulation in a comfort range
that is a function of work effort, and finally, active heat dissipation
by evaporative cooling from regurgitated honey sac contents. The
body temperatures maintained differ depending on caste and expected
foraging rewards.[4]
The
optimal air temperature for foraging is 2225 °C (7277
°F). During flight, the rather large flight muscles create heat,
which must dissipate. The honey bee uses a form of evaporative cooling
to release heat through its mouth. Under hot conditions, heat from
the thorax is dissipated through the head; the bee regurgitates
a droplet of hot internal fluid a "honeycrop droplet"
which immediately cools the head temperature by 10 °C
(18.0 °F).[5]
Below
710 °C (4550 °F) bees become immobile and above
38 °C (100 °F) bee activity slows. Honey bees can tolerate
temperatures up to 50 °C (122 °F) for short periods.
Queens
Periodically, the colony determines that a new queen is needed.
There are three general triggers.
- The
colony becomes space-constrained because the hive is filled with
honey, leaving little room for new eggs. This will trigger a swarm
where the old queen will take about half the worker bees to found
a new colony, leaving the new queen with the other half of worker
bees to continue the old colony.
- The
old queen begins to fail this is thought to be recognized
by a decrease in queen pheromones throughout the hive. This situation
is called 'supersedure; at the end of the supersedure, the old
queen is generally killed.
- The
old queen dies suddenly this situation is known as 'emergency
supersedure'. The worker bees will find several eggs or larvae
of the right age-range and attempt to develop them into queens.
Emergency supersedure can generally be recognized because the
new queen cells are built out from regular cells of the comb rather
than hanging from the bottom of a frame.
Regardless
of the trigger, the workers develop the larvae into queens by continuing
to feed them royal jelly which triggers an extended development
as a pupa.
When
the virgin queen emerges, she is commonly thought to seek out other
queen cells and sting the infant queens within. It is also thought
that, should two queens emerge simultaneously, they will fight to
the death. Recent studies, however, have indicated that as many
as 10% of Apis mellifera colonies may maintain two queens. The mechanism
by which this occurs is not yet known, but it has been reported
to occur more frequently in some South African subspecies of Apis
mellifera.[citation needed] Regardless, the queen asserts her control
over the worker bees through the release of a complex suite of pheromones
called queen scent.
After
several days of orientation within and around the hive, the young
queen flies to a drone congregation point (a site near a clearing
and generally about 30 feet (9.1 m) above the ground) where the
drones from different hives tend to congregate in a swirling aerial
mass. Drones detect the presence of a queen in their congregation
area by her smell, and then find her by sight and mate with her
in mid air (drones can be induced to mate with "dummy"
queens if they have the queen pheromone applied). A queen will mate
multiple times and may leave to mate several days in a row, weather
permitting, until her spermatheca is full.
The
queen lays all the eggs in a healthy colony. The number and pace
of egg-laying is controlled by weather, availability of resources
and the characteristics of the specific race of honey bee. Honey
bee queens generally begin to slow egg-laying in the early fall
and may even stop during the winter. Egg-laying will generally resume
in late winter as soon as the days begin to get longer and peak
in the spring. At the height of the season, the queen may lay over
2500 eggs per day more than her own body mass.
The
queen fertilizes each egg as it is being laid into worker size cell
using stored sperm from the spermatheca. Eggs, laid into drone size
(larger) cells are left unfertilized. The unfertilized eggs have
only half as many genes as the queen or worker eggs and develop
into drones.
Genome
The European honey bee is the third insect, after the fruit fly
and the mosquito, to have its genome mapped. According to the scientists
who analysed its genetic code, the honey bee originated in Africa
and spread to Europe in two ancient migrations.[6] They have also
discovered that the number of genes in the honey bees related to
smell outnumber those for taste, and they have fewer genes for immunity
than the fruit fly and the mosquito.[7] The genome sequence revealed
several groups of genes, particularly the genes related to circadian
rhythms, were closer to vertebrates than other insects. Genes related
to enzymes that control other genes were also vertebrate-like.[8]
The
genome is unusual in having very few transposons, while they have
been present in the evolutionary past (inactive remains were found)
and in general evolved slower than in Diptera species.
Pheromones
Honey bees use special pheromones, or chemical communication, for
almost all behaviors of life. Such uses include (but are not limited
to): mating, alarm, defense, orientation, kin and colony recognition,
food production, and integration of colony activities. Pheromones
are thus essential to honey bees for their survival.
Communication
Honey bees are an excellent animal to study with regard to behavior
because they are abundant and familiar to most people. An animal
that is disregarded every day has very specific behaviors that go
unnoticed by the normal person. Karl von Frisch, who was awarded
the Nobel Prize for physiology and medicine in 1973 for his study
of honey bee communication, noticed that bees communicate through
the language of dance. Honey bees are able to direct other bees
to food sources through the round dance and the waggle dance. The
round dance tells the other foragers that food is within 50 meters
of the hive, but it does not provide much information regarding
direction. The waggle dance, which may be vertical or horizontal,
provides more detail about both the distance and the direction of
the located food source. It is also hypothesized that the bees rely
on their olfactory sense to help locate the food source once the
foragers are given directions from the dances.
Another
signal for communication is the shaking signal, also known as the
jerking dance, vibration dance, or vibration signal. It is a modulatory
communication signal because it appears to manipulate the overall
arousal or activity of behaviors. The shaking signal is most common
in worker communication, but it is also evident in reproductive
swarming. A worker bee vibrates its body dorsoventrally while holding
another honey bee with its front legs. Jacobus Biesmeijer examined
the incidence of shaking signals in a foragers life and the
conditions that led to its performance to investigate why the shaking
signal is used in communication for food sources. Biesmeijer found
that the experienced foragers executed 92.1% of the observed shaking
signals. He also observed that 64% of the shaking signals were executed
by experienced foragers after they had discovered a food source.
About 71% of the shaking signal sessions occurred after the first
five foraging success within one day. Then other communication signals,
such as the waggle dance, were performed more often after the first
five successes. Biesmeijer proved that most shakers are foragers
and that the shaking signal is most often executed by foraging bees
over pre-foraging bees. Beismeijer concluded that the shaking signal
presents the overall message of transfer work for various activities
or activity levels. Sometimes the signal serves to increase activity,
when bees shake inactive bees. At other times, the signal serves
as an inhibitory mechanism such as the shaking signal at the end
of the day. However, the shaking signal is preferentially directed
towards inactive bees. All three types of communication between
honey bees are effective in their jobs with regards to foraging
and task managing.
"The
general story of the communication of the distance, the situation,
and the direction of a food source by the dances of the returning
(honey bee) worker bee on the vertical comb of the hive, has been
known in general outline from the work of Karl von Frisch in the
middle 1950s."
Beekeeping
The honey bee is a colonial insect that is often maintained, fed,
and transported by beekeepers. Honey bees do not survive individually,
but rather as part of the colony. Reproduction is also accomplished
at the colony level. Colonies are often referred to as superorganisms.
Honey
bees collect flower nectar and convert it to honey which is stored
in their hives. The nectar is transported in the stomach of the
bees, and is converted to honey through the addition of various
digestive enzymes, and by being stored in a "honey cell"
and then partially dehydrated. Nectar and honey provide the energy
for the bees' flight muscles and for heating the hive during the
winter period. Honey bees also collect pollen which supplies protein
and fat for bee brood to grow. Centuries of selective breeding by
humans have created honey bees that produce far more honey than
the colony needs. Beekeepers, also known as "apiarists,"
harvest the honey.
Beekeepers
often provide a place for the colony to live and to store honey.
There are seven basic types of beehive: skeps, Langstroth hives,
top-bar hives, box hives, log gums, D.E. hives and miller hives.
All U.S. states require beekeepers to use movable frames to allow
bee inspectors to check the brood for disease. This allows beekeepers
to keep the Langstroth, top-bar, and D.E. hives freely, but other
types of hives require special permitting, such as for museum use.
The type of beehive used significantly impacts colony health and
wax and honey production.
Modern
hives also enable beekeepers to transport bees, moving from field
to field as the crop needs pollinating and allowing the beekeeper
to charge for the pollination services they provide.
In
cold climates some beekeepers have kept colonies alive (with varying
success) by moving them indoors for winter. While this can protect
the colonies from extremes of temperature and make winter care and
feeding more convenient for the beekeeper, it can increase the risk
of dysentery (see the Nosema section of diseases of the honey bee)
and can create an excessive buildup of carbon dioxide from the respiration
of the bees. Recently, inside wintering has been refined by Canadian
beekeepers, who build large barns just for wintering bees. Automated
ventilation systems assist in the control of carbon dioxide build-up.
Products
Pollination
The honey bee's primary commercial value is as a pollinator of crops.
Orchards and fields have grown larger; at the same time wild pollinators
have dwindled. In several areas of the world the pollination shortage
is compensated by migratory beekeeping, with beekeepers supplying
the hives during the crop bloom and moving them after bloom is complete.
In many higher latitude locations it is difficult or impossible
to winter over enough bees, or at least to have them ready for early
blooming plants, so much of the migration is seasonal, with many
hives wintering in warmer climates and moving to follow the bloom
to higher latitudes.
As
an example, in California, the pollination of almonds occurs in
February, early in the growing season, before local hives have built
up their populations. Almond orchards require two hives per acre
(2,000 m² per hive) for maximum yield and so the pollination
is highly dependent upon the importation of hives from warmer climates.
Almond pollination, which occurs in February and March, is the largest
managed pollination event in the world, requiring more than one
third of all the managed honey bees in the United States. Massive
movement of honey bee are also made for apples in New York, Michigan,
and Washington. And despite the inefficiency of honey bees in pollinating
blueberries,[9] huge numbers are also moved to Maine for blueberries,
because they are the only pollinators that can be relatively easily
moved and concentrated for this and other monoculture crops.
Commercial
beekeepers plan their movements and their wintering locations with
prime reference to the pollination services they plan to perform.
Bees,
as well as some other insects, are particularly beneficial as pollinators
to most plants, as they maintain flower constancy, which means they
are more likely to transfer pollen to other conspecific plants.[10]
Also, flower constancy prevents the loss of pollen during interspecific
flights and pollinators from clogging stigmas with pollen of other
flower species.
Honey
Honey is the complex substance made when the nectar and sweet deposits
from plants and trees are gathered, modified and stored in the honeycomb
by honey bees. Honey is a complex biological mixture that consists
mostly of inverted sugars, primarily glucose and fructose. It has
antibacterial and antifungal properties and will not rot or ferment
when stored under normal conditions. However, honey will crystallize
with time. Crystallized honey is not damaged or defective in any
way, for human use, but bees will automatically remove crystallized
honey from their hive and discard it, since they can only use liquid
honey.
Beeswax
Worker bees of a certain age will secrete beeswax from a series
of glands on their abdomen. They use the wax to form the walls and
caps of the comb. When honey is harvested, the wax can be gathered
to be used in various wax products like candles and seals.
Pollen
Bees collect pollen in the pollen basket and carry it back to the
hive. There, pollen is used as a protein source necessary during
brood-rearing. In certain environments, excess pollen can be collected
from the hives. It is often eaten as a health supplement.
Propolis
Propolis is a resinous mixture that honey bees collect from tree
buds, sap flows, or other botanical sources. It is used as a sealant
for unwanted open spaces in the hive. Propolis is marketed for its
alleged health benefits, but may cause severe allergic reactions
in some individuals.
Royal
Jelly
Royal jelly is a honey bee secretion that is used in the nutrition
of the larvae. It is marketed for its alleged health benefits, but
may cause severe allergic reactions in some individuals.
Hazards
and Survival
European honey bee populations have recently faced threats to their
survival. North American and European populations were severely
depleted by varroa mite infestations in the early 1990s, and US
beekeepers were further affected by colony collapse disorder in
2006 and 2007.[12] Chemical treatments against Varroa mites saved
most commercial operations and improved cultural practices. New
bee breeds are starting to reduce the dependency on miticides (acaracides)
by beekeepers. Feral bee populations were greatly reduced during
this period but now are slowly recovering, mostly in areas of mild
climate, owing to natural selection for Varroa resistance and repopulation
by resistant breeds. Further, insecticides, particularly when used
in violation of label directions, have also depleted bee populations[citation
needed], while various bee pests and diseases are becoming resistant
to medications (e.g. American foulbrood, tracheal mites and Varroa
mites).
Environmental
Hazards
In North America, Africanized bees have spread across the southern
United States where they pose a small danger to humans, although
they may make beekeeping difficult and potentially dangerous (particularly
hobby beekeeping).
As
an invasive species, feral honey bees have become a significant
environmental problem in places where they are not native. Imported
bees may compete with and displace native bees and birds, and may
also promote the reproduction of invasive plants that native pollinators
do not visit. Also, unlike native bees, they do not properly extract
or transfer pollen from plants with poricidal anthers (anthers that
only release pollen through tiny apical pores), as this requires
buzz pollination, a behavior which honey bees rarely exhibit. For
example, honey bees reduce fruiting in Melastoma affine (a plant
with poricidal anthers) by robbing stigmas of previously deposited
pollen.
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