How Wild Bees Carry Pollen
Pollination occurs when a bee carries pollen from the anther of a flower to its stigma – the flower's female reproductive organ. Bees do not intentionally carry out pollination; it is the unintended result of the bee’s travels. Pollen clings to the branched and sticky hairs of the bee's body, and is rubbed off as the bee walks or flies from one blossom to another.
Bees carry pollen in order to transport it back to their nests. Pollen is stored in various forms, usually for feeding to the bees' young after they hatch. In most wild bee species, only female bees carry and store pollen. Males of many species drink nectar from flowers, but lack attributes that allow them to transport pollen.
IDENTIFYING BEES BY HOW THEY POLLINATE
Female bees of varying species have evolved singular methods of transporting pollen. Female honey bees and bumble bees, for example, carry pollen in baskets called corbiculae. A corbicula is made up of hairs blended together to form a concave shape.
Most wild bees lack pollen baskets. Instead, many wild female bees have specialized leg hairs called scopae that are particularly long or sticky. Often, the hairs on bees' legs, bodies and faces have a slight electrostatic positive charge; negatively-charged pollen is thus attracted to the hairs.
Particular families and species of bees can be recognized by the distinctive ways in which they carry pollen. Female Andrena mining bees, for example, are said to carry pollen "under their armpits" -- that is, stuffed up against the inside upper surfaces of their back legs.
Bees in the family Megachilidae, such as leafcutter, mason, resin and carder bees, transport pollen on long scopal hairs on their abdomens, as shown in the photo gallery below. This distinctive trait also aids in such bees' identification.
A few bee varieties lack visible attributes for carrying pollen. One is yellow-faced bees, also known as masked bees. These carry pollen internally, in a special organ designed for that purpose. Thus the bees lack the external hairs characteristic of most bees.
NOT ALL BEE SPECIES POLLINATE FLOWERS
Most bees nourish themselves and their young by sipping nectar or gathering pollen from flowers. A few bee varieties, known collectively as cuckoo bees, however, do not collect pollen and thus do not have hairy bodies or pollen-collecting features.
Cuckoo bees survive by raiding the nests of pollen-bearing bees, where the cuckoos deposit their eggs. When the cuckoo young merge, they devour the pollen stores left by the hosts for their own offspring. Sometimes the cuckoos kill off the hosts' young as well.
PHOTOGRAPHIC GALLERY OF POLLINATORS
Below is a gallery of photographs showing different types of bees and the specialized ways in which they have evolved in order to transport pollen.
Female honey bees carry pollen in corbiculae, or pollen baskets, located on the bees' back legs. The corbiculae are made of tightly-woven leg hairs.
The color of the pollen in a bee's baskets varies from flower to flower. Here, a honey bee is gathering the bright red pollen of bottlebrush buckeye.
Bumble bees, like honey bees, carry pollen in corbiculae. This is a female common eastern bumblebee, transporting orange sage pollen in pollen baskets located on the bee's hind legs.
Wild bees that lack pollen baskets often transport pollen on sticky hairs, called scopal hairs, located on their hind legs. This species, Melissodes subillata, is a kind of true long-horned bee.
This is another kind of true long-horned bee, a Melissodes trinodis. This species' scopal hairs are particularly feathery and visibly branched.
Bushy back-leg scopal hairs are in fact a defining trait of true long-horned bees, one which aids in their identification.
This is an Andrena mining bee. These bees are said to carry pollen "in their armpits," stuffed under the top inner sides of their back legs.
This is an Andrena mining bee in a tree poppy -- the bee's underarm scopal hairs are so laden with pollen that it appears to have rolled in yellow flour.
Pollen color sometimes aids in bee identification. This spring beauty mining bee specializes in the woodland bulb known as spring beauty, which produces pale pink pollen. This mining bee thus can bee recognized in part by the color of the pollen it carries.
Mining bees' thoraxes often are covered with fairly dense and long hairs. The hairs are electrostatically charged, and thus the bees inadvertently pick up pollen on their thoraxes while intentionally loading it onto their back legs.
Pollen clinging to mining bees' thoraxes rubs off as the bees fly from flower to flower, thus aiding in pollination.
Male and female bees tend to differ in appearance because female have pollen-carrying apparati on their legs, while males do not. This female Wilkes' mining bee, for example, has bushy hairs on its back legs.
This is a male Wilkes mining bee. Note that the bee's hind leg is thin and lacking in bushy scopal hairs.
This is a male Carlin's mining bee foraging for nectar on snow drop bulbs. Note that the bee's back leg appears thin and that its hairs are not particularly long or bushy -- they are ill-equipped for carrying pollen.
This is the same Carlin's mining bee. Although the bee does not have leg scopae, when it stopped to sip nectar from a snow drop, the bee's positively-charged thorax hairs attracted negatively-charged pollen from the flower. Thus, inadvertently, the male bee may pollinate another snow drop as it continues foraging.
This is a male miserable mining bee -- despite its lack of scopal hairs, the bee is covered in electrostatically-charged dandelion pollen. Thus, as it continues on to another flower, the bee may pollinate other dandelions.
This is a female sweat bee (Halictus rubicundus) loading pollen onto its back legs.
Pollen also clings to the sweat bee's face after she drinks nectar. This pollen will be carried to another blossom, possibly resulting in its pollination.
This female Georgian mason bee carries pollen on bright orange scopal hairs located under its abdomen.
This is a close-up of the mason bee's scopal hairs. This peculiar way of carrying pollen is a defining trait of bees belonging to the family Megachilidae, which aids in their identification.
This is a female flat-tailed leafcutter bee. Like female mason bees, female leafcutter bees can be recognized quickly by the long scopal hairs under their abdomens, used to carry pollen.
This is a close-up of the falt-tailed leafcutter's scopal hairs.
This is a view of the flat-tailed leafcutter bee's scopal hairs from underneath.
The color of underside scopal hairs differs among leafcutter species. This is a female alfalfa leafcutter bee, with predominantly white scopal hairs.
Pollen clings to the alflfa leafcutter's scopal hairs, as shown here.
As the bee flies back to its nest, the pollen clings remarkably well to the scopal hairs, without falling off.
Resin bees also transport pollen under their abdomens. This giant resin bee (Megachile sculpturalis) has black and brownish scopal hairs.
This is an ant-sized yellow-faced bee (Hylaeus modestus). This bee carries pollen internally, in an organ specially designed for this purpose. This attribute makes this species less vulnerable to pollen-theft by larger bees.
This is a kind of cuckoo bee called a nomad bee (Nomada articulata). The bee looks wasp-like, because it lacks pollen-carrying hairs. This species robs pollen from the nests of mining bees.
This Triepeolus remigatus cuckoo bee is also wasplike in appearance, because it lacks visible hairs. This bee raids the nests of squash bees.
Bees as a rule have a "furry" appearance. Hair on all parts of a bee's body serves to attract pollen. This female true long-horned bee (Melissodes trinodis) has particularly feathery, branched hairs on her hind legs that allow her to carry large pollen loads.
This is a common eastern bumblebee (Bombus impatiens), carrying orange pollen in corbiculae, or pollen baskets. The corbiculae are made of densely woven hairs on the bee's hind legs.
This is a Georgian mason bee (Osmia georgica). Mason, leafcutter, carder and resin bees, all members of the family Megachilidae, carry pollen on scopal hairs located on the undersides of the bees' abdomens.
Male bees lack special pollen-collecting hairs, but nonetheless may transport pollen inadvertently. This male Carlin's mining bee (Andrena carlini) has been sipping nectar from snow drops. The bee's positively-charged thorax hairs have attracted negatively-charged yellow snow drop pollen -- despite the fact that the bee is not gathering pollen intentionally. When the male bee flies to another snow drop blossom, the pollen may rub off and coincidentally pollinate it.
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