Pollinia

Until yesterday, pollinia were vaguely remembered structures encountered only in obscure books. Then I saw some.

One often sees a solitary bee covered in pollen (first picture). Also, one often sees a female bumble bee carrying a pollen ball on its hind legs (second picture). The bumble bee collects pollen and packs it into a ball on (what is called) its corbicula for transportation back to the nest. In each of these cases, the pollen is collected from the flower as individual grains.

Pollinium (pl: pollinia): a mass of pollen grains fused by means of their wavy texture or fine threads, It originates from a single anther. This mass sticks together and during pollination is transported as a single unit.

It came as a surprise to me yesterday to see quite a few bumble bees transporting pollen a different way (final pictures). In truth, I first thought those yellow pellets between the wings were mites attacking the bees. But no, they are pollinia. Lincoln Best set me straight.

Some flowers don’t spread individual pollen grains to a pollinator such as a bee. Rather the flower packs many grains into a bundle, a pollinium, which it then glues onto the back of the bee. When the pollinia–packing bee visits another flower, some of the individual pollen grains brush off, but the rest of the pollinium stays in place to travel to other flowers on the bee’s back.

Wild orchids, periwinkle, and dogbane package their pollen in this way. But, what flower supplied the pollinia seen in these pictures remains unclear. Could there be some fairy slippers blooming this early? Does anyone know?

A small solitary bee (Andrena sp.) is covered in pollen.

A Bombus morissoni has packed pollen into a ball on its hind legs.

This Bombus mixtus is carrying some pollinia between her wings.

Here is a rear view of the mixtus more clearly showing two yellow pollinia.

Another bumble bee (a Bombus vagans?) is carrying pollinia on its back as it flies to a dandelion.