Apiculture Factsheet #111
Bee Behaviour During Foraging
Insect pollinators, including honeybees, evolved together with
flowering plants for millions of years. Plants developed floral
parts with increasingly specialized features to attract visiting
insects who, in turn, would distribute pollen grains and optimize
the plant’s reproductive capabilities. Simultaneously, these
wasp-like insects underwent physiological adaptations to take
advantage of the nutritional benefits offered by flowering plants.
Physical adaptations were augmented by changes in foraging and
nesting behaviour that proved mutually beneficial to flora and fauna.
Some of the physical adaptations of the honeybee include:
Each compound eye is spherical in shape and comprised of
some 6,300 cone-shaped facets or eyes. Bees can easily distinguish
high contrast shapes and patterns. The visual spectrum of the
honeybee has shifted towards shorter wavelengths, enabling it to
detect ultra-violet, while red, with its longer wavelength, appears as
a dull grey. Bees are particularly sensitive to blue, yellow and
blue-green colours even though bees can detect light intensity only
1/20 as well as humans.
The sensitivity to ultra-violet and polarized light enables the
honeybee to observe the sun under cloudy conditions. Its
spherical-shaped eyes allow the honeybee to measure angles
accurately between the relative positions of the sun, the food
source and the nest. These field observations are then interpreted
and communicated to other bees inside the hive through a 'dance'.
Scout bees can direct their fellow worker bees to the location of a
food source, negating the need for each individual to search. Unlike
most other insect pollinators, the adaptation of communication has
enabled honeybees to utilize floral resources of a large area. As a
result, honeybee colonies can attain a biomass at the height of
season far greater than any other pollinating insect. Bumble bees
and all solitary bees do not communicate and hence, each individual
relies on its own foraging success. The foraging range of these
pollinators is limited to a comparatively small area.
The honeybee’s olfactory sense is estimated to be 40 times
better than man’s and plays a critical role in locating food sources
and communication in and outside the nest. Some 5,000 - 6,000 olfactory
detectors are on each antenna.
Taste is detected through the mouthparts and forelegs.
Bees have a limited range of taste and many substances detected by
humans are tasteless to bees. Within the narrow range of substances
they can taste, bees display high sensitivity. Sugar solutions as
low as 2% can be detected although for foraging purposes, bees are
not interested unless the sugar concentration is 30% or more.
Sense of Time
Bees are known to be time sensitive.
Communication inside the nest expressing the location of a site
relative to the sun has been observed over time, even when the sun's
position progressed below the horizon. Awareness of time is
important in determining the time of nectar secretion and the
commencement of foraging.
Economics of Foraging
Foraging requires energy and the
honeybee's evaluation as to where, what and how long to forage is
all related to the economics of energy consumption and the net gain
of food to the colony. For example, foraging bees may not access a
high quality food source because its distance requires energy
expenditure exceeding the energy value of the food source. Generally
bees fly only as far as necessary to secure an acceptable food
source from which there is a net-gain. Factors that influence
foraging behaviour and determine profitability:
- weather e.g. wind,
temperature, and sunlight,
- distance of the food source from the
hive (including differences in elevation),
- food quality
(concentration of sugar, protein content of the pollen),
- quantity of nectar or pollen.
Bees are known to fly as far as 12 km (8 miles),
but usually foraging is limited to food sources within 3 km.
Approximately 75% of the bees from a colony forage within one
kilometre while young field bees only fly within the first few
Foraging bees tend to limit their visits
to a single species of plant during each trip. This behavioural
adaptation is critically important for plants since it assures the
transfer of pollen from one plant to another plant of the same
species. In commercial crops, foraging constancy is essential for
optimizing seed set and fruit development.
Individual foragers will acquire a sample through scouting in the
morning and tend to fly to the same source as long as it remains
profitable. Bees will shift to another plant species if the nectar
or pollen fails. Even then, memory will cause these foragers to
return several times and re-check. In areas with great floral
diversity and small plantings, a higher percentage of foraging bees
will visit different kinds of plants during the same trip. This
would account for the mixed pollen loads of returning bees.
Speed of Work
Bees visit up to about 40 flowers per minute
depending on floral type, nectar availability and weather
conditions. Floral visitation rate by honeybees of some important
- apricots 10 sec
- apples 68 sec
- cherries 82 sec
- raspberry 116 sec
- black currant 134 sec
The longer the time period, the greater the nectar availability. It
takes twice as much time to collect a load of nectar compared with a
load of pollen.
Honeybees are foraging generalists and capable of utilizing a
wide range of floral sources. On the other hand, many insect
pollinators are specialists and only visit certain floral sources.
Foraging specialization by the insect coincides with higher
efficiency of utilizing the food source, which means
improved pollination for the plant. For example, bumblebees evolved in bog
environments of temperate zones where the principal nectar and
pollen sources are characterized by long colliery floral tubes and
bloom during cool and wet spring conditions. Furthermore, pollens of
these sources are generally moist and sticky. Bumble bees have
developed a long proboscis (tongue), are highly pubescent (hairy) to
forage under inclement weather, and are capable of
"buzzing" while on the flower to cause the release of
pollens. As such, bumblebees have proven highly efficient in crops
such as blueberry, cranberry and blackberry.
- Below 8 C - no foraging
- 8 C - 16 C -
- 16 C - 32 C - optimal conditions
- Above 32 C -
reduction in foraging, increase in water collection.
Speed of Flight
- Loaded bee - approx. 25 km/h (15 mph) on
- Empty bee leaving hive - 20 km/h (12.5 mph) on average.
Increased wind reduces foraging activity. At a wind speed of 40
km/h (25 mph) foraging will stop.
Number of Trips per Day
The number of trips will depend on
various conditions including weather, forage availability, strength
of colony, etc. In general, 5-15 trips are made while a water
collector may make as many as 100 trips per day.
The nectar flow is the period when bees forage and collect nectar
to sustain the colony. The nectar flow is the period when there is
such an abundance in nectar production that the bees gather a surplus
beyond the immediate needs of the colony, which is converted to
honey and stored in the combs. To optimize the nectar resource of an
area, the beekeeper must be thoroughly familiar with the vegetation,
its condition and blooming time.
Locating the Nectar
Nectar and pollen sources are located by any foraging bee and not
limited to scout bees. After finding a valuable food source, the bee
will return to the colony and communicate its finding to other bees
through a 'bee dance'. Carl von Frisch first described this form of
communication, expressing direction, distance and food quality.
The bee's specialized tongue, called the proboscis, is a suction
pump. The nectar passes through the esophagus into the nectar sac
where a valve prevents the nectar from passing into the digestive
stomach or ventriculus. The nectar sac is essentially a widening of
the esophagus and functions as a collecting chamber of liquid foods
during transportation. The weight of a full nectar sac may be as
much as 90% of the body weight of the bee.
During the return trip to the hive, saliva is added to the nectar
which contains the enzyme invertase. Invertase reduces complex
sugars into simple sugars, which is part of the conversion from
nectar into honey. Should the bee require more energy for the flight
home, the valve between the nectar sac and the ventriculus will open
allowing nectar to pass into the digestive stomach.
A field bee carrying only nectar will fly with the rear legs wide
Handling Nectar on Return to the Hive
After return to the hive, the forager passes the nectar on to
'house' bees. She opens her mandibles with her proboscis retracted,
and a drop of liquid appears at the base of the glossa while the
house bee extends her proboscis fully, and sucks up the drop. The
speed of food transmission and processing is determined by various
factors, including temperature, the age of the bees, colony
strength, its food reserves and the total colony intake of nectar
During a strong nectar flow the partly ripened honey is stored in
the cells of the comb immediately, or after only a few transfers
from bee to bee. During a moderate or weak flow the food is passed
on to and by many bees before it is stored. The greater the number
of bees in the chain, the richer the ripe honey will be in their
secretions and hence in enzymes.
Partially processed nectar or raw honey contains too much water.
Water is removed through evaporation during the ripening process,
which involves two phases.
A bee, actively involved in processing nectar, pumps out the
contents of her nectar sac into a flat drop on the underside of the
proboscis which she then draws up again. This back-and-forth action
is repeated rapidly for 15-20 minutes. The liquid is thereby exposed
to the warm air of the hive, causing evaporation. In this way, the
bees produce half-ripened honey containing about 50-60% (maximum
70%) of dry substance.
The second, passive phase of honey ripening involves the deposit
of half-ripened honey in small droplets on the cell walls, or in a
thin film on the cell floor. As a rule, 1/4 to 1/3 of the cell is
filled; but during a strong flow, or if there is lack of space, 1/2
or 3/4 of each cell is filled straight away. Normally, when the
honey is nearly ripe, the bees move it again, and the cells are then
filled to 3/4 of their capacity. The final ripening takes 1 - 3
days, depending on the water content when the honey is first put
into the cells, the level to which the cells are filled, the amount
of air movement achieved, and temperature and relative humidity.
Under good conditions the % of water in the honey will be reduced to
below 20% in about 4 days.
The rate of evaporation from cells 1/4 full is three times that
of cells filled 3/4 full. When adequate comb space is available few
cells are more than half full. As moisture is evaporated, bees fill
cells, leaving empty cells to receive more green nectar. It is
important to have adequate empty comb space during the nectar flow
to prevent crowding.
Pollen Collecting and Storage
Pollen is dislodged from the anther of the flower and adheres to
the branched hairs of the bee. The tongue and mandibles (jaws) are
often used to lick and bite the anther. Pollen becomes stuck to the
mouthparts and is moistened. While the bee is resting or hovering in
the air she removes the pollen from her body and transfers it to the
corbicula (pollen basket) of her rear legs.
The process involves all of the bee's three pairs of legs. The
wet pollen is removed from the mouthparts, head and antenna by the
forelegs. Small amounts of nectar are used to moisten the pollen
mixture. The second pair of legs (mid legs) comb pollen from the
underside of the thorax and receive it from the forelegs. The inside
of the basi-tarsi of the rear legs contain combs which remove the
pollen from the brushes of the mid legs. By rapidly rubbing the hind
legs, pollen is gradually moved up to the opening between the basi-tarsus
and tibia of the rear leg. The rake of the opposite leg will then
force the pollen into the corbicula or "pollen basket". A
pollen load contains up to 10% nectar, which is necessary for
In the hive, pollen is removed from the rear legs by a spike on
the mid legs and is placed in cells. Often the head is used to pack
the pollen in cells. Honey is added to maintain pollen quality. This
final product is called bee bread.