There are four natural resources required by honeybees for
survival: water, resin, nectar, and pollen (Seeley 1985).
Water is used to cool the hive and to dilute the honey fed to
the larvae. Resin is utilized to reinforce the hive, seal off
decaying wood, and plug up holes. Nectar is the major source
of carbohydrates from which honeybees obtain their energy.
Nectar is collected by foraging worker bees and is carried
back to the hive in their honey stomachs. Upon returning to
their hive, the nectar is usually transferred to hive workers
for processing into honey, although it can be fed directly to
the brood or to the adults (Winston 1987). Enzymes from the
bee's hypopharyngeal glands are added to the nectar in the
bee's crop. These enzymes break down the nectar into simple
forms of sugars, which are easier for the bees to digest.
These enzymes, in addition to the high sugar content, also
protect the stored honey from bacteria. The water in the
nectar is then evaporated off of the worker's tongue. The
nectar is placed into cells and fanned to further reduce
water in it. Through this process, the water content in
the nectar is reduced to less than 18% (Winston 1987).
Once the evaporation process is complete, the nectar is
considered "ripened" and is called honey. The cell is
capped with wax until the honey is needed for feeding to
the larvae or the adults.
Some statistics about honeybees and the production of honey
are important to note. Years of observation and research
have revealed a number of facets about this subject. For
example, it is estimated that to make one pound of honey,
honeybees must visit about two million flowers, fly a total
of about 50,000 miles, and carry about 37,000 loads of nectar
back to the hive. According to the British entomologist,
Arthur Thomson, during the main flower blooming periods it
is common for the bees from a single hive to visit as many
as 250,000 flowers during the course of a single day (Teale
1942). Some flowers, such as the ones of a tulip tree
(Liriodendron tulipifera) each produces about a teaspoon
of nectar. Other flowers, such as the ones of white clover
(Trifolium repens), produce only enough nectar to cover
1/20 of a pinhead (Crane 1975).
Each worker bee is able to carry a load of nectar equal to
one-half its total weight and during her lifetime one worker
will collect enough nectar to produce about 1/12 of a teaspoon
of honey. During nectar
gathering, a honeybee consumes 0.5 mg of ripe honey per
kilometer of flight. To produce one liter of surplus honey
the worker bees of a hive will consume eight additional
liters of ripe honey as food. Ripened honey and pollen stored
in a hive are the food sources eaten by the bees. Feeding a
bee larva from the egg to maturity requires about 142 mg of
honey (Winston 1987).
Where does the pollen in honey come from?
Pollen is the bee's major source of proteins, fatty substances,
minerals, and vitamins (Gary 1975). It is essential for the
growth of larvae and young adult bees (Dietz 1975). Honeybees
remove pollen from an anther by using their tongue and mandibles.
While crawling over flowers, pollen adheres to their "hairy" legs
and body. The honeybee combs pollen from her head, body, and
forward appendages, mixes it with pollen from her mouth, and
transfers it to the corbicula, or "pollen basket", on her
posterior pair of legs. When "loaded" with pollen, she will
return to her hive. Once at the hive, workers pack the pollen
into the comb. To prevent bacterial growth and delay pollen
germination, a phytocidal acid is added to the pollen as it is
packed into the comb. Other enzymes produced by worker bees
are also added which prevent anaerobic metabolism and fermentation
thereby enhancing the longevity of the stored pollen. Once
completely processed for storage, the pollen comb is referred
to as "bee bread" and is ready for later consumption by the bees.
The protein source needed for rearing one worker bee from larval
to adult stage requires approximately 120 to 145 mg of pollen
(Alfonsus 1933; Haydak 1935). An average size bee colony
will collect about 20 to 57 kg of pollen a year (Armbruster
1921; Eckert 1942). In most cases the primary foraging areas
for pollen are the various insect-pollinated plants bees visit
for nectar. However, honeybees will also visit a number of
species of wind-pollinated plants for which their only purpose
is to collect pollen. Wind pollinated species of Salix (willow),
Quercus (oak), Celtis (hackberry), and many species of grasses
(Poaceae) as well as some of the wind-pollinated types of
composites (Asteraceae) are considered important pollen sources
for foraging honeybees.
Melissopalynology is the study of pollen in honey. For over
100 years the literature pertaining to the study of pollen in
honey has been termed or spelled several ways, including:
mellissopalynology, mellittopalynology, and melittopalynology.
According to Paxton's Botanical Dictionary (1868), both "melissa"
and "melitta" mean "a bee". The scientific name of the honeybee
is Apis mellifera L. The word "melliferous" comes from
the Latin word mellifer (honey) and the suffix -ous meaning
"having, full of, or characterized by". The International
Commission for Bee Research uses "melissopalynology",
which is the term used throughout this essay.
Pollen can be incorporated into the honey produced in a
beehive in a number of ways. When a honeybee lands on a
flower in search of nectar, some of the flower's pollen is
dislodged and falls into the nectar that is sucked up by the
bee and stored in her stomach. At the same time, other pollen
grains often attach themselves to the hairs, legs, antenna,
and even the eyes of visiting bees. Later, some of the pollen
that was sucked into her stomach with the nectar will be
regurgitated with the collected nectar and deposited into
open comb cells of the hive. While still in the hive the
same honeybee might groom her body in an effort to remove
entangled pollen on her hairs. During that process pollen
can fall into open comb cells or the pollen can fall onto
areas of the hive where other bees may track it into regions
of the hive where unripe honey is still exposed in open comb
cells. Some worker bees also collect pollen for the hive.
The smooth, slightly concave, outer surfaces of the hind tibia
in worker bees are fringed with long hairs that curve over
the tibia surface to form a hollow area. This hollow area is
called the "pollen basket" or orbicular. The worker bees
collect pollen with their front and middle legs and then
deposit it in their cubicula (Snodgrass and Erickson 1992).
In the process of depositing collected pollen into special
comb cells some of it can fall into the hive or into open
honeycombs. It is also noted that occasionally worker bees
might add pollen to the nectar they are transforming into honey.
Airborne pollen is another potential source of pollen in honey.
Many types of airborne pollen produced mostly by wind-pollinated
plants that are not usually visited by honeybees can enter a
hive on wind currents. These airborne pollen grains are
usually few in number, when compared to the pollen carried
into the hive by worker bees, nevertheless, those pollen
types regularly enter a hive on air currents and can settle
out in areas where open comb cells are being filled with nectar.
Sometimes airborne pollen is deposited into ripened honey when
it is being removed from a hive by the beekeeper. Although the
pollen rain for various regions consists mainly of airborne
pollen, and those data are often used in forensics, archaeology,
and ecology to identify a specific geographic region, those
pollen data are not always as useful in melissopalynology because
they generally form only a minor (?) fraction of the total
pollen spectrum found in a honey sample.
Pollen is an essential tool in the analyses of honey. Taxa
of pollen are used to indicate the floral nectar sources utilized
by bees to produce honey (Lieux 1975, 1977, 1978; Moar 1985;
Louveaux et al. 1970; Sawyer 1988; Van der Ham et al. 1999).
Thus, the relative pollen frequency is often used to verify
and label a honey sample as to the major and minor nectar
sources. This information has important commercial value
because honey made from some plants commands a premium price
(i.e., sourwood, tupelo, buckwheat, or citrus honey). Even
non-premium grades of honey require certain types of
verification because they must be correctly labeled before
being marketed. Identifying and quantifying the pollen in
honey samples is one of the best ways to determine the range
of nectar types used to produce a honey, and therefore label
it correctly based on actual foraging resources. Another
reason that pollen analyses of honey are often required is
to identify the geographical source of origin. The combination
of wind and insect-pollinated taxa found in a honey sample
will often produce a pollen spectrum that is unique for the
specific geographical region where it was produced. Because
of trade agreements, import tariffs, and legal trade restrictions,
most of the leading honey-producing nations of the world
require accurate labeling of honey before it can be sold. This
is especially true for the EEU that has had strict labeling
regulations for honey products since 1974 (EEU 2001).
The history of melissopalynology: a brief overview
At the end of the nineteenth century, Pfister (1895) examined
the pollen contents of various Swiss, French, and other European
honeys. Through his analysis, he demonstrated the possibility
of determining the geographical origin of honey from the pollen
within it. He was able to identify many of the pollen grains
he found because of earlier studies of pollen morphology,
structure, and identification of European pollen types by
botanists including Guillemin in 1825, Fritsche in 1832, Mohl
in 1834, and Fischer in 1890 (Wodehouse 1935).
The history of the scientific investigation of U.S. honey begins
in the early 1900s when a researcher working for the United
States Department of Agriculture (USDA), W. J. Young, published
a brief report on the analysis of domestic honey produced in
the United States (Young 1908). One of the reasons that Young
says he examined the pollen content of honey was to determine
if pollen studies could be used in the future to "judge the
adulteration of a sample" (Young 1908). His hypothesis was
that if honey was adulterated with sugar syrup, this could be
detected by finding a reduction in contents of the pollen.
However, the method he used to determine the pollen concentration
values of his samples is not considered accurate by today's
standards. Currently, most melissopalynologists use larger
amounts of a honey sample (10 g) and ratios of pollen grains
per gram of honey based on counts derived from comparing the
pollen to percentages of introduced "tracer" spores added to
each sample before analysis. Young, on the other hand,
determined his published pollen concentration ratios for
19 of his 100 honey samples by extracting only one gram of
honey from each sample, diluting it with water, and then
counting a small portion. He doesn't explain why he did not
attempt pollen concentration studies for the other 81 samples
in his study. When deriving his concentration values, Young
relied on identifications of pollen types that still contained
their pollen's cytoplasm, waxes, or surface lipids. By failing
to process the honey samples in order to remove those components
from the pollen, Young's ability to make precise identifications
of pollen types was probably difficult. Young states that he used
the pollen concentration value for each of his 19 samples as a
basis for predicting the expected pollen concentration values
for future studies of each type. Based on his work, Young
determined that the range of pollen concentration values
varied from a low of 123 pollen grains/g to a high of 5,410
grains/g of honey.
The second reason Young examined the pollen contents of his
100 samples was to determine the identity of "the pollen
from a large number of flowers known or suspected to be
visited by bees in different sections of the country"
(Young 1908). Ninety of the 100 honey samples had a
purported source that was provided by the beekeeper, such
as "melon honey, clover honey, or cotton honey", etc. The
other 10 honey samples were listed as being from mixed floral
sources. Thus, for each of the 100 samples the major pollen
types were compared to see if they corresponded with the
suspected honey source. For example, each of his pollen
analyses reported first the sample number followed by the
type of purported honey based on the report provided by the
beekeeper that collected the sample. Next, Young listed
the state in which the honey was collected and then the
pollen types he found in the sample. Each of his entries
is listed such as this one: "sample 61. Melon (Illinois).
Clover, Melon, Cruciferous, Polygon um, Alfalfa, Basswood,
Composite (two kinds), and Ellipsoidal types". Unfortunately,
Young provides no explanation as to how many pollen grains
he counted for each sample, nor the percentage of each pollen
type he identified. He also does not say if the pollen list
for each sample is based on the descending order of pollen
frequency of each type found in the sample.
Although Young's report focused mainly on the chemical
aspects of honey and honeydew samples,
he was one of the first to examine the pollen contents of
honey. He made a key to the pollen grains commonly found in
U.S. honey, discussed the importance of protecting honey
samples from airborne contaminants, and discussed the various
kinds of structures (insect parts, fragments of the comb,
fungal spores, dust, pollen, etc.) that are likely to be
encountered when examining honey. Nevertheless, his actual
pollen data are of little research value to melissopalynologists
today. Unfortunately, Young provides no explanation as to
how many pollen grains he counted for each sample, what was
the relative percentage of each pollen type he listed, or even
which pollen types were the most or least important in each sample.
In 1911, Fehlman published his work on the pollen spectra found
in various examples of Swiss honey (Maurizio 1951; Maurizio and
Louveaux 1965; Lieux 1969). Fehlman's work was significant
because he was the first European to use pollen as a way to
identify and differentiate honeydew from nectar honeys, and to
demonstrate that pollen contents were the key to determining the
nectar sources in honey samples.
In the United States during the 1920s Parker (1923) conducted a
study of bees and the honey they collect. His research remains
an important contribution for a number of reasons. First, he
described 28 different kinds of pollen collected by honeybees,
and included photographs of the 12 most important ones. Second,
like others before him, Parker was convinced that the pollen
content in honey was a valuable tool for identifying the foraging
sources used to make it. Third, he recognized that if bees were
trapped on their return to the hive, the pollen recovered from
the nectar in their honey stomach would identify the foraging
areas being utilized by the hive.
Other research advancements in melissopalynology during the 1920s
were made by Betts and Allen, who worked separately on English
honey. Betts (1923, 1925) made sketches of 15 different kinds
of pollen sources found in English honey types and she suggested
that flowers from herbarium specimens could be used as a source
of pollen to make comparative reference samples. These
taxonomically-correct pollen reference samples, she reasoned,
would speed the identification of unknown types found in
English honey and it would also enable researchers to add
another level of precision to their identification of pollen
recovered in honey samples. A few years later, Allen (1928a)
noted that some pollen grains remain on the surface of the
honey, instead of becoming mixed with the honey like other
types of pollen. Allen reasoned that some pollen grains
"floated" on the surface of honey because they must be lighter
and less dense than the honey. He was also the first to report
that pollen found mixed with nectar could come from sources
other than the nectar plant's own anthers and pollen (1928b).
For example, Allen observed that accidental contamination of
nectar and eventually the honey it was used to produce could
occur through several means. First, he noticed that bees that
had visited one type of flower might move to flowers of a
different plant species in search of new nectar sources.
If that occurred, then pollen adhering to the body of the
bees could accidentally fall into, and thereby contaminate
the nectar of the second flower type with pollen from previously
visited plants. Allen also noted that airborne pollen could
easily contaminate honey when combs were being removed from
hives and also during the subsequent honey extraction process.
Regardless of the causes and types of pollen contamination,
however, Allen reasoned that contamination was usually a minor
problem and that pollen in honey mostly reflected the actual
floral sources used to make the honey.
By the end of the 1920s Allen (1929) was focusing on some of the
problems of conducting accurate melissopalynology analyses.
He was the first researcher to caution about some of the pitfalls
and difficulties of pollen identification in melissopalynology.
For example, Allen noticed that dried pollen on herbarium sheets
and fresh pollen collected in flower anthers looked very
different from the pollen he recovered in honey. As a result
of his observations, he was the first to question the accuracy
of pollen identifications reported from other previous
melissopalynology studies. Allen published a series of
articles in Bee World (1928a, 1938b, 1928c, 1928d; 1929)
where he illustrated that many of the pollen types found in
honey samples look nearly identical and that various pollen
genera could easily be mistaken for other pollen types because
many of them looked superficially similar. Finally, he noted
that because the predominant types of mounting media fixed both
pollen reference material and pollen recovered from honey samples
in permanent positions on a microscope slide, the pollen grains
could not be rolled over in order to search for a critical aperture
or morphological feature that would confirm the type's true
identity. The final contribution of Allen's work (1928a, 1938b,
1928c, 1928d; 1929) was his proposed pollen classification system
for English honey. In one article, for example, he cautioned that,
"one should doubt the origin of a honey sample as being English if the
sample contains six-grooved pollen grains". Today, we know that those
pollen types are common among the genera in the family Lamiaceae and
include taxa such as Mentha (mint), Thymus (thyme),
and Salvia (sage).
Introduced species of many of those plants now grow in English gardens,
thus Allen's initial conclusions would no longer be valid.
During the 1930s and 1940s one name stands out as being the leader
in melissopalynology research. Zander's (1935, 1937, 1941, 1949,
1951) five-volume work, published over a span of nearly two decades,
laid the foundation for melissopalynology research in Europe.
In his various analyses and reports he includes descriptions,
drawings, and photographs of pollen that he found in various
types of European honey. He also includes several studies of other
types of material that are sometimes recovered in honey, such as
fungal spores and hyphae. Because of his long and dedicated works
in the field, Maurizio and Louveaux (1965) refer to him as the
"leader in melissopalynology research in Europe".
In the United States the period of the 1930s represented a time
when no research in melissopalynology was being conducted even
though some additional research continued on plants used as honey
sources. It was during the early 1930s that two valuable books on
honey plants were first published: American Honey Plants (Pellett
1930) and Honey Plants of Iowa (Pammel et al. 1930). Later, in
1939, Oertel published the results of his seven-year study on the
sources and blooming periods of plants thought to be principal
honeybee nectar sources in various regions of the United States
During the early 1940s two scientists working for the USDA in California,
Frank Todd and George Vansell, began searching for the relationship and
importance of pollen in honey (Todd and Vansell 1942). Their research
began when they discovered that bee colonies would survive, but would
not reproduce if they were fed only sugar syrup. Once pollen was
added to the feeding syrup egg laying in the hive began with 12 hours.
Their multi-year study represents the next major study in melissopalynology
in the United States after Young's 1908 initial examination of pollen
grains found in domestic honey. Todd and Vansell restricted their
pollen and nectar research to plants and honey produced in California,
because that is where their laboratory was located and they could
get assistance in their study from experts at the University of California.
The two researchers began their study by collecting and examining over
2,600 individual samples of nectar. One of their goals was to try to
determine the number of pollen grains one should expect to find in
1cc of nectar from each different plant species. Next, they wanted
to determine if the number of pollen grains found naturally in nectar
samples matched the number of pollen grains found in the honey
stomachs of bees that foraged on those same nectar types. Third,
they wanted to discover how efficiently bees could remove pollen
from the nectars they collected.
The Todd and Vansell (1942) study was virtually ignored when it was
first published, but the importance of their work has now been
recognized as significant because of the information they collected
and the implications their data provided about pollen counts in honey.
Nevertheless, Todd and Vansell admit that some of their research ideas
came from a study in Wisconsin by Whitcomb and Wilson (1929), who had
been studying dysentery in honeybees when they noticed that many of
the pollen grains sucked into a bee's honey stomach along with nectar
were quickly removed through a process of filtering. Whitcomb and
Wilson noted that once nectar enters a bee's honey stomach it is filtered
and within 10 minutes most of the pollen in the nectar is removed leaving
mostly pure nectar in the honey stomach. They concluded that the
ability of a bee to filter nectar in her honey stomach is one way of
removing unwanted debris from nectar, such as pollen and fungal spores,
which might germinate and spoil future honey made from the gathered
The honeybee's filtering process, as described by Snodgrass and
Erickson (1992) is rapid and effective. The bee sucks nectar into
a slender tube that ends in the bee's abdomen where it becomes an
enlarged thin-walled sac called the honey stomach. This thin-walled
sac is greatly distensible and can expand to hold large amounts of
nectar. Once in the honey stomach, the nectar flows over the
proventriculus which serves as a regulatory apparatus that filters
and controls the entrance of food into the bee's stomach.
The anterior end of the proventriculus, also called the honey
stopper, projects into the bee's honey stomach like the neck of a
bottle and at its anterior end is an x-shaped opening consisting of
four, thick, triangular-shaped, muscle-controlled lips. The nectar
in the honey stomach is drawn back and forth into the funnel-shaped
proventriculus where it is filtered to remove debris such as pollen
grains and the fungal spores of foul brood. The posterior end of
the proventriculus extends into the anterior end of the ventriculus
that is part of the bee's alimentary canal (mid gut) where digestion
and food absorption occurs. A valve at the bottom of the proventriculus
prevents the filtered nectar from entering the bee's digestive
system and it ensures that the nectar is returned to the honey stomach.
However, this same valve will open to allow debris removed from the
nectar to pass into the bee's alimentary canal and then pass into
the intestines where it is stored in the rectum until it is excreted.
From time to time people get alarmed about a phenomenon referred
to as "yellow rain" (Newman 1984). Yellow rain is nothing more
than bee feces. When large numbers of bees forage on nectar
sources containing high quantities of pollen, the rapid removal
of those pollen grains from their honey stomachs quickly fills
their rectums. The result can be rapid defecation by those swarms
of bees as they return to the hive. If the flight path of the bees
happens to be over urban areas, their feces, or "yellow rain",
may leave hundreds of tiny yellow spots on cars, sidewalks, or
The development and use of pollen coefficients in melissopalynology
One of the primary goals of Todd and Vansell (1942) was to determine
how effectively honeybees could remove pollen from their honey stomachs,
how long that pollen removal process took, and if all pollen types
were removed equally well by the filtering process of a bee's honey
stopper. In one experiment they fed a laboratory beehive diluted
unifloral star thistle (Centaurea) honey that had been produced by
bees foraging in the wild. The star thistle pollen concentration
in the honey-water mixture was measured as being 5,200 pollen grains
per cc. Later, the sealed honeycomb cells produced by caged honeybees
feeding on this honey-water source were removed and examined. Todd and
Vansell found that instead of an average of 5,200 star thistle pollen
grains per cc, the produced honey contained an average of only 1,200
pollen grains per cc. Even though Todd and Vansell had expected the
pollen concentration of the newly produced honey to remain constant,
they found that it did not. In another experiment Todd and Vansell
mixed three grams of pure pollen (the pollen type they used is not
mentioned) with 100 cc of water-diluted syrup. When measured, they
found the pollen concentration of the diluted syrup solution was
750,000 pollen grains per cc. After allowing honeybees to feed
on that mixture as frequently as they wanted, the researchers removed
honeycomb cells made from that syrup and discovered that the pollen
concentrations of the new honey were only 25,000 pollen grains per cc.
In other words, the honeybees drank a diluted syrup solution containing
a pollen concentration of 750,000 pollen grains per cc, then, using
their internal honey stomach filtration system those bees removed
most of the pollen before emptying their honey stomachs into new
comb cells. The result was a newly produced honey containing only
1/30th of the original pollen concentration of the diluted syrup.
Although these researchers' goals were not to develop pollen coefficient
tables, their pioneering effort led others to use their ideas and
experimental data to compile lists of plants that are over or under
represented by their pollen in honey samples (Maurizio 1949, 1955,
1958; Berner 1952; Pritsch 1957; Deans 1957; Demianowicz 1961, 1964;
and Sawyer 1988) and propose pollen coefficient tables for various
types of nectar-producing plants.
Demianowicz (1961, 1964) is one of the early melissopalynologists
who worked tirelessly for many (13) years trying to solve the problem
of accurate unifloral honey classification based on pollen contents.
After examining many honey samples Demianowicz realized that the
relative pollen count in honey did not always reflect the primary
floral and nectar sources. Demianowicz's summarized data appear in
her 1964 publication where she attempts to identify the pollen
characteristics of 45 different types of unifloral honey that are
common to various regions of Europe. For each unifloral type she
used caged bees in small hives of only 300-400 workers and one queen.
The bees in each caged hive were allowed to feed on the flowers of
only one plant species. Thus, the honey each hive produced was
considered to be a valid representation of the expected absolute
pollen concentration (APC) for the flower type being tested. Based
on that research, she developed 18 different categories of plants
based on whether their APC values in honey are under or over
represented. For each category she assigned an "average number"
that she called her "pollen coefficient classes". She believed
that the newly established pollen coefficient values could be used
as a guide for determining the true unifloral nature of a honey
sample, regardless of the data represented by the relative pollen
In Demianowicz's table of values she says that the expected APC
of pollen types in a "class 1 unifloral type" should not be
expected to be higher than 740 pollen grains per 10 g of honey.
Her key example of an under represented type in class 1 is
Asclepias (milkweed) which has an assigned pollen coefficient
value of 32. Each additional class is represented by APC values
that are up to twice as high as the previous category. Thus, in
her class 2 of unifloral honey types she says that genera in this
group should contain between 750-1,500 pollen grains per 10 g of
honey. Plant examples in this second category include
Robinia pseudoacacia (white acacia, locust), Cucumis
(cucumber), and Chamaenerio (Epilobium) (fireweed).
The last of her coefficient categories is class 18, which is
characterized by prolific pollen types, such as Myosotis
(forget-me-not ), which produce unifloral honeys containing
between 98,304,001 to nearly 200 million pollen grains
per 10 g.
Many melissopalynologists have worked on the problem of trying
to discover how to use pollen contents to classify various types
of unifloral honey even though experimental data (Todd and Vansell 1942)
show that plants produce different amounts of pollen and that
bees will remove vast amounts of pollen from collected nectar on
their flights back to the hive. Nevertheless, a number of
scientists have produced tables and charts noting what they
believe should be the "expected" percentages of relative pollen
in unifloral types. Moar (1984) offers one of the clearer
discussions about the process that he used to establish pollen
coefficient tables for various types of unifloral honey in New
Zealand. Moar points out that since 45% of a single pollen type
is the universal "minimal" amount needed for a honey to be
classified as unifloral, one must determine what value must
be used to correct an under represented unifloral pollen type
to the 45% level. Next, he points out that he and others believe
that the relative pollen values for white clover (Trifolium repens)
are the best standard upon which all other types in honey samples
must be judged. Therefore, it is chosen to be the standard pollen
type for determining the coefficient values of all other pollen types.
Moar notes that the expected absolute pollen concentration of
Trifolium repens pollen should be approximately 23,116 grains
per 10 g of honey. However, Moar fails to explain exactly how he
determined this figure to be the APC value for T. repens. For
example, Demianowicz's (1964) research with caged bees revealed
that 18,000 should be considered the APC for a unifloral honey of
T. repens. Perhaps the differences between these two
researchers derive from their different methods of calculating
the APC value for T. repens. One of the most widely used
calculation methods is to add a known number of "tracer spores"
to 10 g of honey and then determine the ratio of tracer spores
to pollen in the honey. Once this ratio is known for a sample,
then the APC for any pollen taxa in the sample can also be determined.
Demianowicz's calculation method is different. For each of her
honey samples she began with a known amount of honey that was
diluted with a known amount of water. From that mixture she
extracted a small portion and counted the pollen. From that
count she then predicted what the total APC for each pollen
type should be per 10 g of honey.
In his 1985 article on the honey of New Zealand, Moar explains
how he calculated the minimum percentage of unifloral honey types.
For his example of an under represented type he used thyme (Thymus)
pollen. He says his first task was to find examples of honey that
was produced by hives located close to fields of blooming thyme.
If the honey from those hives had the color and taste of thyme honey,
then they were assumed to be unifloral examples of thyme honey.
Moar found four samples of honey that fit these criteria. When he
conducted a pollen study of these, he found that the relative
pollen percentage averaged 42%, even though the totals varied
slightly in each sample. He also averaged the pollen concentration
values in the four thyme samples and found that the APC of thyme
pollen was 5,415 pollen grains per 10 g of honey. Because the
relative pollen percentage of thyme was less than the minimum of
45% needed for a unifloral classification, Moar multiplies the
thyme's APC by 0.45 and then divides by the average relative
pollen frequency, (0.42) of thyme in the four samples. That
math calculation produced the number 5,801, which Moar points
out should be considered as the appropriate "corrected" APC for
thyme pollen at the minimum unifloral level of 45%. Nevertheless,
because thyme pollen is an under represented taxon in honey (i.e.,
any taxon with an APC lower than the APC of white clover), a
further calculation was needed to determine the minimal percentage
of thyme pollen in the relative pollen count of a honey sample
before the sample could be classified as being unifloral thyme.
Moar then notes that because the APC of white clover is considered
the standard, the ratio of thyme's APC of 5,801 to the APC (23,116)
of white clover must be determined. This is calculated by dividing
the APC for thyme (5,801) by the combined APC of thyme and white
clover (5,801 + 23,116). That number (0.2), two-tenths, is then
multiplied by 100 to convert it to a percentage (20%). As Moar
explains, the use of these calculations reveal that for New Zealand,
a relative pollen percentage of only 20% thyme pollen in a honey
sample would qualify that honey as being a unifloral thyme honey.
One of the foremost melissopalynologists in the United Kingdom (U.K)
is Rex Sawyer who began his lifelong interest in pollen studies
during the 1930s after meeting Harry Godwin, the British pioneer
of pollen analysis. Later, Sawyer began a study of beekeeping
and helped Deans (1957) compile a detailed pollen study of honey
types produced in the U.K. After years of melissopalynology
research Sawyer published several books on pollen and honey
(Sawyer 1981, 1988). In one of them (Sawyer 1988) he includes
a chapter on pollen coefficients and lists a table of numerical
pollen coefficient (PC) values that he developed and believes
can be applied to the relative pollen percentages of various
pollen types in honey samples. The table is impressive, yet
Sawyer fails to explain exactly where or how he arrived at
the precise PC values that he published. His only reference
to this is a note saying that his values are based on APC data
from his own research and from various other studies including
the research of: Todd and Vansell (1942), Demianowicz (1961, 1964),
Maurizio (1949, 1955, 1958), Berner (1952), and Pritsch (1957).
The primary difference between the PC values used by Sawyer and
those published by other melissopalynologists is that Sawyer's
values are not expressed as the expected APC per gram of honey
for each taxon whereas others all use APC values per 10 g of honey.
Nevertheless, by using Sawyer's formula and applying his PC numbers
to the relative pollen percentages of a honey sample one can
determine the "actual" floral identity and characteristics of
almost any honey sample. Sawyer notes that once the expected
relative pollen percentages for key pollen taxa are determined
for a honey sample, it is possible to use his formula and PC
values to calculate the "corrected percentages" for nearly all
pollen types found in both unifloral and mixed floral honeys.
He also notes that since he did not calculate the PC values for
all known pollen types in honey, he recommends using a PC value
of 50 for all unidentified pollen types and pollen taxa that
appear in sporadic or low frequencies.
The result of Sawyer's research led to the establishment and use
of his table of pollen coefficient numbers for honey types in the
UK as well as elsewhere. As Sawyer and others have argued,
through the use of pollen coefficient tables analysts can confirm
unifloral honey samples produced from plants with low pollen
yields or plants which produce pollen types that seem to be
most quickly removed by the filtering actions of a honeybee's
honey stopper during her return flight to the hive. As noted
in Sawyer's list, some of the weakest-represented pollen types
are aided by the use of pollen coefficient values. These would
include fireweed (Epilobium), basswood (Tilia), alfalfa
(Medicago), sourwood (Oxydendron), orange blossom (Citrus),
buckwheat (Eriogonum), and locust (Robinia pseudoacacia).
When pollen coefficient tables are applied to correct the normally
low relative pollen percentages, of up to 20%, for these types
in honey samples, the result becomes a validation that the honey
should indeed be classified as a unifloral product of those plants.
An example of how pollen coefficient tables developed by
Sawyer (1988) can be used is seen in Table 1. The data in
Table 1represent the analysis of a typical fireweed honey sample
from central Alaska. Note that based on the relative percentages
of pollen, this sample would initially be classified as a "uniflora"
canola honey. Note also that the relative percentage of fireweed
pollen in this sample is only 6.3%. When these relative pollen
percentages are adjusted using Sawyer's pollen coefficient values,
it suggests that the actual nectar sources used to produce this
honey were really 95% from fireweed flowers, and only 2% from
rapeseed (canola) flowers. These pollen data suggest that in
spite of the low relative pollen percentage of fireweed, the
dominant nectar resource that produced this honey came from
blooming fireweed flowers. Note also in this example (Table 1)
that the 28.3% relative pollen percentage of clover suggests
that actually less than 2% of the nectar source of this honey
came from clover.
One of the main problems of using pollen coefficient tables is that
not all melissopalynologists agree on precisely what values
should be assigned to each plant and pollen type used by bees
to produce honey. For example, if we examine the same data
listed in Table 1, but instead use those relative pollen
percentages with the pollen coefficient values developed by
Demianowicz (1964), we find that the adjusted percentages of
nectar sources for each taxon is different from those of Sawyer's
|Pollen analysis of a honey sample produced in central Alaska.*
|* To use pollen coefficient tables to determine the
actual or expected nectar composition of each plant taxon in a honey
sample, the relative pollen spectrum must first be calculated. Next,
the relative percentage of each pollen type must be divided by
its pollen coefficient value (Sawyer 1988). The resulting value
for each pollen type is what Sawyer calls the taxon's "relative
quantity". Finally, the percentage of each pollen type's relative
quantity is used to determine what percentage of the honey is
derived from the nectar represented by each taxon.
When examining the "adjusted percentages" calculated using Sawyer's data
and those derived from Demianowicz's data we can see minor differences;
nevertheless, both sets of data offer the same conclusion. In terms of
over or under representation, both sets of data indicate the same
general conclusions for each pollen taxon. For example, using Sawyer's
PC values it appears that over 95% of the actual nectar source came from
fireweed flowers, but when using Demianowicz's values it appears that
only 80% of the nectar source came from fireweed flowers. There is a
difference of 15% between the two calculations, yet both sets of data
emphasize that fireweed is a pollen type that is highly under represented
in honey samples. Similar conclusions can be reached for each of the
other pollen types as well.
|In the example below we have used the same
relative pollen percentages shown for taxa in Table 1. As Sawyer
(1988) recommends, we have used the baseline PC value of Trifolium repens
for unknown pollen types or pollen types for which no PC values
were determined by Demianowicz (1964). In the formula below, "A"
represents the adjusted percentage for each pollen taxon.
|Aa = (a/PCa)/(a/PCa + b/PCb + c/PCc + d/PCd + ........ n/PCn)
|Aa = .000033/(.000033 + .000872 + .005600 + .000393 + .000033 + .000077)
|Aa = .000033/.007008
|Aa = .005 = .47%
|a = Apiaceae||00.6||00.47||00.50
|b = Brassica||62.8||12.44||01.90
|c = Epilobium||06.3||79.90||95.90
|d = Melilotus||28.3||05.60||01.70
|e = Taraxacum||00.6||01.09||00.27
|f = unknown||01.4||00.47||00.12
It is difficult to know which of these PC data sets (Sawyer vs.
Demianowicz) is more nearly accurate. Demianowicz's PC values are
based on more than 13 years of research in which she used caged
bees and forced each hive to feed only one type of flower. From
those data she constructed her APC and PC values. We are not sure
which data Sawyer used to construct his PC values. However, based
on her published reports we do know the method Demianowicz (1961,
1964) used for calculating pollen concentration values in her
study and we also know that her method is subject to more potential
calculation errors than most of the currently-used pollen concentration
techniques. Demianowicz's method for determining pollen concentration
values relied on collecting small amounts of honey (often less than
5 grams) and then diluting her sample with water. From the diluted
solution she then placed one drop on a microscope slide and counted
a portion of the pollen on the slide. Using that information she
then projected what the expected APC values for each pollen taxon
should be in 10 g of honey. By contrast, today most melissopalynologists
calculate pollen concentration values by comparing the ratio of pollen
grains found in 10 g of honey against the ratio of a know number of
tracer spores that are added to the honey before counting begins.
Depending on the number of tracer spores added and the number of
pollen grains counted, this system is considered to provide more
nearly accurate data than the system used by Demianowicz.
Other melissopalynologists (D'Albore 1998; van de Ham et al. 1999)
have not proposed pollen coefficient tables but do list a wide
variety of plant types, which they place into various categories
depending on the "expected" pollen, yield of those plants in
various types of honey. For example, van de Ham et al. (1999)
mentions that honey types can be considered unifloral examples
if they contain a minimum of: 1) Borago [borage] 10%; 2) Robinia
[white acacia, locust], Tilia [linden, basswood], and Carduus
[distel, thistle] 20%; and 3) Crambe [krambe, sea kale] and
Calluna [heather] 30%. They also state that for some plants
the APC of their pollen is so prolific in honey that one should
not consider those honey types as unifloral unless they contain
significantly more than the normally required minimum of 45%.
Some of those over-represented pollen types they mention include:
1) Salix [willow] 70%; and 2) Phacelia [bluebells], Myosotis
[forget-me-not] and Castanea [chestnut, chinkapin] each at 90%.
D'Albore (1998) does not give lists of percentage levels that he
believes should be used as a guide for determining unifloral honey
in the Mediterranean region based on the under or over-representation
of pollen taxa. Nevertheless, he offers some practical advice about
a number of plant taxa and how the pollen from those taxa is likely
to be represented in honey samples. He notes that most of the plant
group that produces large pollen grains (>40 m) will be significantly
under represented in honey produced from those nectar sources. The
two reasons he gives for this are: 1) most plants that produce large
pollen grains generally do not produce large quantities of nectar,
and 2) honeybees are much more efficient at filtering out large
pollen grains than small ones from the nectar in their honey stomach
during their return flights to the hive. D'Albore adds that the
opposite is true for tiny pollen grains, which are most often over
represented in honey. Tiny pollen grains from species including
Echium [gran canaria], Eucalyptus [gum], Amorpha [indigo], Castanea
[chestnut, chinkapin], and Tamarix [salt cedar], he notes, are often
produced in larger numbers and those tiny grains are only partially
filtered out of the honey stomach of honeybees returning to the hive.
In his book he also lists a large number of plants in the Mediterranean
region that produce pollen, which tends to be either over or under
represented in honey samples for a variety of reasons. The reasons
he lists include: 1) plants that normally produce small amounts of
pollen (i.e., Citrus, Robinia, Salvia); 2) plants that are monoecious
and thus only one half of the flowers produce pollen (i.e., Citrullus
[watermelon], Cucumis [cucumber], Cucurbita [pumpkin or gourd],
Bryonia [bryony]); 3) plants that have flowers that are morphologically
unfavorable for pollen collection by honeybees (i.e., Asphodelus
[affofill], Epilobium [fireweed], Abutilon [mallow], Datura [datura],
Digitalis [foxglove]); and 4) plants that present special pollen and
nectar gathering problems for honeybees or have plants that are difficult
for honeybees to enter (i.e., Agrostemma [corn cockle], Cestrum [cestrum],
Nicotiana [tobacco], Medicago [alfalfa]).
Todd and Vansell's (1942) research revealed other important variables
that will determine the amounts and types of pollen recovered from honey
samples. In one experiment they starved a group of honeybees and then
allowed them to drink freely from solutions of sugar syrup mixed with
various amounts of pollen. After feeding a control group of bees was
immediately trapped and dissected. The content of their honey stomach
was removed and examined for pollen. Bees that fed on the syrup-pollen
mixture had an average of 248,666 pollen grains per cc of fluid in their
honey stomachs. Forty-eight other bees that fed on the same syrup-pollen
solutions were allowed to fly around freely for 15 minutes after feeding
before being caught and dissected. The same procedure was used to
determine the pollen concentration values of the fluid in their honey
stomachs. As noted in those tests, almost one-half of the honeybees
were able to remove and excrete more than 90% of the pollen they had
consumed when feeding on the syrup-pollen solutions. The other bees
that were tested in that experiment also removed much of the pollen.
These data suggest that even though all 48 of the bees in this experiment
collected nectar containing the same amount of pollen, some of them
were much more effective at removing pollen with their honey stoppers
than were others from the same hive. This variable makes the reliability
of using a standard set of numbers for pollen coefficient tables difficult.
For any given honey sample the accurate calculation and use of corrective
PC values are nearly impossible unless the melissopalynologist knows how
many honeybees collected nectar for each source, how many of those honeybees
removed what percentage of the pollen from the nectar they collected,
and how long each honeybee took on her return flight to the hive after
filling her honey stomach full of nectar. Since these types of nectar
gathering data can only be estimated for any hive or any type of honey
a hive produces, the use of PC tables could vary the results greatly
from one sample to the next even if all examined honey samples were
produced from the same nectar sources, but for some samples those
sources were located at different distances from the hive.
Todd and Vansell repeated this same experiment with different pollen
concentrations in a sugar syrup solution that they fed to honeybees.
In all their tests they found that the amount of pollen still present
in the honey stomachs of bees allowed to fly freely for 15 minutes after
feeding was drastically reduced. Although the results varied from bee
to bee, Todd and Vansell reported that many of the bees had an ability
to remove at least 90% of the pollen from the fluid in their honey stomach
during a 15-minute interval after feeding on nectar containing pollen.
Another contribution of the Todd and Vansell (1942) study was the
development of a table revealing how many pollen grains occur naturally
in the nectars of certain plants. Because flower nectar sources
are usually close to the dehiscing anthers of those same flowers,
some of the anther pollen falls into the nectar that is later gathered
by honeybees. Todd and Vansell carefully collected the nectar from
more than 2,600 samples representing 73 different plant species that
grow in California. Some of those samples were collected from the honey
stomachs of bees that were captured and dissected immediately after
they fed on the nectar of a specific plant. Other samples were
carefully collected by hand from the nectar of actual flowers.
After all the samples were examined and the pollen concentrations of
each nectar source were averaged, the authors produced a list of
some of the major California nectar sources and the amount of pollen
that one might expect to find in the nectar of those plants. That
list is important because it offers a perspective as to which nectar
types are known to contain vast amounts of pollen and which nectar
sources do not. For example, Todd and Vansell report that they captured
and dissected 30 honeybees immediately after each had finished feeding
on orange blossoms (Citrus sinensis) and they also collected a set of
32 bees immediately after each had fed on cotton flowers (Gossypium
hirsutum). To their amazement, they could not find one single pollen
grain in the honey stomachs of any of those 62 honeybees. At the other
extreme, they found an average of 7,100 pollen grains per cc of fluid
in the honey stomachs of 38 bees captured immediately after each had
completed feeding on the nectar of rabbit brush (Chrysothamnus nauseosus).
In another experiment Todd and Vansell examined what happens to pollen
between the time it is collected as part of the nectar from a flower
until it becomes honey sealed in the comb chamber of a hive. They
deprived the honeybees in a hive of stored honey but allowed them to
feed from trays placed in the hives that were filled with a solution
of sugar syrup mixed with pollen. They repeated the same experiment
in a different hive using a tray of diluted star-thistle honey placed
in the hive. Measurements of the pollen in the feeding trays revealed
a pollen concentration value of 750,000 pollen grains/cc for the tray
of syrup mixed with pollen and 5,200 pollen grains/cc for the feeding
tray of diluted star-thistle honey. During both experiments the bees
were not allowed to feed on any other sources of food. Honey produced
in the sealed comb cells made from these two solutions revealed a pollen
concentration of 25,300 pollen grains/cc for the honey made from the
syrup-pollen solution and 1,200 pollen grains/cc for the honey made
from diluted star-thistle honey. Todd and Vansell concluded from these
experiments that only 3.1% of the pollen placed in the syrup-pollen
feeding trays actually appeared in the honey made from that source.
For the honey made from the feeding tray of diluted star-thistle
honey, only 23% of the pollen from the tray appeared in the new combs
of honey. In both experiments the feeding trays were placed in the hives;
therefore, the probable time between each bee's feeding time and when
she regurgitated the contents of her honey stomach into comb cells was
probably minimal. In spite of that suspected short period, it appears
that most of the honeybees in both hives were able to remove vast
amount of pollen from the fluids they ingested before those fluids
were used to make honey.
Following up on this experiment Todd and Vansell tested actual nectar
sources from the flowers of important bee-foraging plants and found an
average of 2,500 pollen grains per cc in purple sage (Salvia leucophylla),
an average of 200 pollen grains per cc in fireweed (Epilobium angustifolium),
an average of 2,000 pollen grains per cc in avocado (Persea americana),
and an average of 41,000 pollen grains per cc in white sweet clover
(Melilotus alba). What those data reveal is that the pollen of some
plants will always be either under or over represented in honey even
if 90% (i.e., average efficiency of pollen removal by most bees based
on experimental data by Todd and Vansell) of the pollen is removed
from the honey stomach of a honeybee returning to the hive. What
these data suggest is that one cc of nectar from sweet clover should
be over 200 times better represented by its pollen in a honey sample
than will an equivalent cc of nectar from fireweed plants.
In recent years the intended purpose of producing and using data that
list over and under-represented pollen types in honey (D'Albore 1998;
van de Ham et al. 1999), or lists that detail the actual pollen
coefficient number for each taxon (Sawyer 1988; Demianowicz 1961,
1964), is to allow individuals to use the relative pollen percentages
from a honey sample to re-calculate the probable (actual?) percentages
of each nectar source used to produce that honey sample. The main
advantage of using these data is to verify unifloral honey types that
command premium prices on the world market even though the relative
pollen counts from such honey samples probably do not contain the
internationally accepted minimum pollen percentage of 45%.
Tables of under and over represented pollen types and pollen coefficient
tables also help to explain why certain popular bee foraging plants are
routinely represented by minimal amounts of pollen in honey that may be
dominated by pollen from other types of over represented bee-foraging
plants such as Melilotus and Brassica. Research on developing better
pollen coefficient tables continues, but some melissopalynologists do
not believe that these types of "correction" tables will ever become
universally accepted. Arguments against the adoption of a standard
set of pollen coefficient tables focus on several factors, which are
rarely known for any given honey sample. For example, as early as
the 1920s scientists knew that the longer nectar remains in a honeybee's
honey stomach, the greater is the potential for that honeybee to
remove most or all of the pollen in that nectar, regardless of the
pollen type (Whitcomb and Wilson 1929). Therefore, knowing the time
period between when a honeybee begins to forage and when she returns
to the hive becomes critical because it will influence the amount of
pollen that remains in the nectar of her honey stomach. That information
is important because it determines the amount of potential pollen
from each floral source that can be included in the honey produced
from each nectar source. The second variable focuses on the size and
shape of the pollen grains being collected along with the nectar from
a floral source. Experimental data reveal that bees are much more
efficient at removing large pollen grains from the nectar in their
honey stomachs than they are for smaller pollen grains (Demianowicz
1961, 1964; D'Albore 1998). The third variable centers on determining
precisely what the corrective PC value for each pollen type should be.
The published data presented by various melissopalynologists state
different APC or PC values for the same or similar plants. Often
these values are somewhat similar, but depending on which APC or PC
values a researcher selects to use, the actual percentage of a single
pollen type needed for a honey to gain a unifloral classification will
The use of corrective pollen values is important for beekeepers, honey
distributors, and for the customer who buys honey for his or her own use.
Unfortunately, much of the existing research in this area of honey studies
suffers from one or more major flaws. Some previous researcher have
not provided critical information on how they gathered, processed, or
counted the pollen in the honey samples they used to establish their
APC or PC tables. Others offer full explanations of their research and
thus reveal the flaws of their methodology. Even the research conducted
by Demianowicz (1961, 1964), which is among the best studies of APC
and PC values yet completed because she used caged bees that ate a
restricted diet, there are flaws in her technique which could have
altered her results.
What is needed most in the field of melissopalynology is a new series
of tests to determine the precise PC values that can be used with
certainty for validating the floral sources of premium types of honey.
This type of research, however, will need to be conducted under controlled
conditions that will satisfy skeptics and produce PC data that will be
accepted by melissopalynologists.
For each floral type a separate experiment will need to be conducted.
First, an isolated hive of bees will need to be caged to prevent outside
contamination, similar to the technique reported by (Demianowicz 1964).
The caged bees should then be allowed to feed freely on the flowers of
only one type of plant until the hive produces a measurable amount of
honey from that single floral source. During the experiment selected
numbers of bees should be trapped immediately after they have fed on
nectar and the contents of their honey stomach must be examined to
determine the APC in the nectar. At various times during the experiment
the opening for bees returning to the hive should be sealed for short
periods of time ranging from 5-15 minutes. Before allowing the bees
to re-enter the hive, some of the bees should be captured and the
contents of their honey stomachs should be examined to determine how
effective those bees have been at removing pollen from the nectar
they are collecting. Finally, once honey has been produced from the
experimental feeding process, several honey samples must be collected,
processed, and their pollen contents counted.
Processing of the collected honey from these caged experiments must
include either a filtration process similar to the one described by
Lutier and Vaissiere (1993), or it must use an alcohol-dilution
technique similar to the one first described by Jones and Bryant (1996).
Later experimental tests conducted by Jones and Bryant (1998)
confirmed that both the filtration and alcohol-dilution techniques
are comparable in the amounts of pollen they recover from honey samples.
Their tests revealed that both the filtration and alcohol processing
methods increased pollen recovery from honey samples by an average of
more than 200% over the various types of water-dilution processing
methods that are currently in use by melissopalynologists. Finally,
a large quantity of tracer spores must be added to each honey sample
before it is processed. The original ratio of tracer spores to pollen
should be nearly equal in each honey sample to ensure that the
construction of APC tables for pollen types are as accurate as
possible. Finally, when counting the recovered pollen from each
honey sample, the ratio of tracer spores to pollen must be based
on high pollen counts in excess of 1,000 pollen grains per sample.
This type of proposed research will be expensive and time consuming.
However, if these research efforts are completed successfully, the
resulting data can be confidently used to construct APC values that
should be accepted by even the most ardent skeptics. In addition
to the APC values, these same honey samples can serve as unique
opportunities for chemical testing to determine sugar types and
the ideal ranges for sugar isotopic levels.
ALLEN, M. Y.
1928a Armchair thoughts. Bee World 9: 57.
1928b Pollen grains. Bee World 9: 66.
1928c Pollen grains II. Bee World 9: 103-105.
1928d Pollen grains III. Bee World 9: 148-151.
1929 Pollen grains IV. Bee World 10: 114-118.
ALFONSUS, E. O.
1933 Zum Pollenverbrauch des Bienenvolkes. Archiv für Bienenkunde 14: 220-223.
1921 Vergleichende Eichungsversuche auf Bienen und Wespen.
Archiv für Bienenkunde 3: 219-230.
1952 Die ausvertung der pollenanalyse. Archiv für Bienenkunde 29:33-38.
BETTS, A. D.
1923 The identification of pollen sources. Bee World 5: 43-45.
1925 Notes on pollen identification. Bee World 7: 90.
1975 Honey, a Comprehensive Survey. Russak & Co., Inc., New York.
D' ALBORE, G. R.
1998 Mediterranean Melissopalynology. Universita Degli Studi di
Perugia, Instituto di Entomologia agrania Publication. Perugia, Italy.
DEANS, A. S. C.
1957 Survey of British honey sources. International Bee Research
Association Circular, London.
1961 Pollenkoeffizienten als Grundlage der quantitativen Pollenanalyse
des Honigs. Pszczelnicze Zeszyty Naukowe 5(2): 95-105.
1964 Characteristik der Einartenhonige. Annales de l'Abeille 7: 273-288.
1975 Nutrition of the adult honeybee. In:
The Hive and the Honey Bee, (Dadant, C., and Dadant, C. P.,eds.),
Dadant & Sons, Carthage, Illinois, p. 125-126.
ECKERT, J. E.
1942 The pollen required by a colony of honeybees.
Journal of Economic Entomology 35: 309-311.
EUROPEAN ECONOMIC UNION
2001 Web site http://europa.eu.int/eur-lex/en/lif/dat/1974/en_374L0409.html
GARY, N. E.
1975 Activities and behavior of honeybees. In: The Hive and the Honey Bee, (Dadant, C., and Dadant, C.P.,eds.), Dadant & Sons, Carthage, Illinois, p. 185-264.
HAYDAK, M. H.
1935 Brood rearing by honeybees confined to pure carbohydrate diet.
Journal of Economic Entomology 29: 657-660.
JONES, G. and BRYANT, V.
1993 Melissopalynology. In: Palynology: Principles and Applications,
(J. Jansonius and D. C. McGregor eds.), pp 933-938. American Association
of Stratigraphic Palynologists Foundation, Dallas, Texas.
1996 Techniques in Melissopalynology. In: New Developments in
Palynomorph Sampling, Extraction, and Analysis (V. Bryant & J. Wrenn, eds.),
pp 107-114, AASP Contribution Series # 33. American Association of
Stratigraphic Palynologists, Dallas.
LIEUX, M. H.
1969 A palynological investigation of Louisiana honeys.
Unpubl. doctoral dissertation, Department of Botany and Plant
Pathology, Louisiana State University, U.S.A., 113 p.
1975 Dominant pollen types recovered from commercial Louisiana
honeys. Economic Botany 29: 78-96.
1977 Secondary pollen types characteristic of Louisiana honeys.
Economic Botany 31: 111-119.
1978 Minor honeybee plants of Louisiana indicated by pollen
analysis. Economic Botany 32: 418-432.
LUTIER, P. M., and VAISSIERE, B. E.
1993 An improved method for pollen analysis of honey.
Review of Palaeobotany and Palynology 78: 129-144.
LOUVEAUX, J., MAURIZIO, A., and VORWOHL, G.
1970 Methods of melissopalynology. Bee World 51: 125-131.
1949 Pollenanalytische Untersuchungen an Honig und Pollenhöschen.
Beihefte zur Schweizerische Bienen-Zeitung 2: 320-412.
1951 Pollen analysis of honey. Bee World 32: 1-5.
1955 Beiträge zur quantitativen Pollenanalyse des Honigs. 2.
Absoluter Gehalt pflanzlicher Bestandteile in Tilia- und Labiaten-Honige.
Zeitschrift für Bienenforschung 3(2): 32-39.
1958 Beiträge zur quantitativen Pollenanalyse des Honigs. 3.
Absoluter Gehalt pflanzlicher Bestandteile in Esparsette, Luzerne,
Orangen und Rapshonige. Annales de l'Abeille 11: 93-106.
MOAR, N. T.
1985 Pollen analysis of New Zealand honey.
New Zealand Journal of Agricultural Research 28: 39-70.
1984 Pollen: breath of life and sneezes.
National Geographic Magazine (October):490-521.
1939 Honey and pollen plants of the United States.
U. S. Department of Agriculture Circular 554, Washington, D. C.
PAMMEL, L. H., and KING, C. M. (eds.)
1930 Honey Plants of Iowa. Iowa Geological Survey Bulletin 7.
State of Iowa, Des Moines, Iowa.
PARKER, R. L.
1923 Some pollen gathered by bees. American Bee Journal 63: 16-19.
PELLETT, F. C.
1930 America Honey Plants, Together with Those Which are of Special
Value to the Beekeeper as Sources of Pollen. (3rd ed.)
American Bee Journal, Hamilton, Illinois.
1895 Versuch einer Mikroskopie des honigs. Forschber.
Lebensmitt. u. ihre Bez. z. Hygiene, Forens. Chem., Pharmakogn.
(2)(1/2): 1-9; 29-35.
1957 Zum problem der mikroskopischen pollenanalyse des
bienenhoring. Wiss. Zs. Humboldt-univers. Berlin 6:197-204.
1988 Honey Identification. Cardiff Academic Press, Cardiff, Wales, UK.
SEELEY, T. D.
1985 Honeybee Ecology. Princeton University Press, Princeton, New Jersey.
SNODGRASS, R.E. and ERICKSON, E. H.
1992 The anatomy of the honey bee. In: Dadant and Sons (eds.)
The Hive and the Honey Bee, Dadant & Sons, Hamilton, Carthage,
Illinois, p. 103-169.
TODD, F. E., and VANSELL, G. H.
1942 Pollen grains in nectar and honey.
The Journal of Economic Entomology 35: 728-731.
VAN DER HAM, R.W.J.M., KAAS, J.P., KERKVLIET, J.D. and NEVE, A.
1999 Pollenanalyse. Stichting landelijk Proefbedrijf
voor Insektenbestuiving en Bijenhouderij Ambrosiushoeve.
Hilvarenbeek, Netherlands. 156 p.
WHITCOMB, W. JR., and WILSON, H.F.
1929 Mechanics of digestion of pollen by the adult
honeybee and the relation of undigested parts to dysentery of bees.
Wisconsin Agricultural Experiment Station Research Bulletin 92.
WINSTON, M. L.
1987 The Biology of the Honey Bee. Harvard University Press, London.
WODEHOUSE, R. P.
1935 Pollen Grains. Hafner, New York.
YOUNG, W. J.
1908 A microscopical study of honey pollen. United States
Bureau of Chemistry, Bulletin 110, Washington, D.C. 93p.
1935 I. Pollengestaltung und Herkunftsbestimmung bei Blütenhonig.
Reichsfachgruppe Imker, Berlin.
1937 II. Pollengestaltung und Herkunftsbestimmung bei Blütenhonig.
Liedloff, Loth, & Michaelis, Leipzig.
1941 III. Pollengestaltung und Herkunftsbestimmung bei Blütenhonig.
Liedloff, Loth, & Michaelis, Leipzig.
1949 IV. Studien zur Herkunftsbestimmung bei Waldhonigen.
1951 V. Letzte Nachträge zur Pollengestaltung und Herkunftsbestimmung
bei Blütenhonig. Liedloff, Loth, & Michaelis, Leipzig.
Author contact: Vaughn M. Bryant, Jr,
Palynology Laboratory, Texas A&M University, College Station, Texas 77843-4352, USA
From CAP Newsletter 24(1):10-24, 2001.