Sunday 24 May 2020

Investigation of the Honeybees Pollen Baskets

In my other role as Keeper of honeybees for the Islay Pollinator Initiative I have come to learn a great deal about flowers and pollination, attentive to what is in flower and the value of each for the honeybee.  There is always a fall off of pollen brought back by the bees and I collect up samples to have a closer look and learn a little more about what they are really foraging on.  Sheltering indoors with Saturday's rainy, windy weather I finally had the chance to look through a scoop of pollen collected from a hive a week or so back that did not make it through the queen excluder the bees were moving through. 

As with all flowers different by colour, shape and texture, so too are the pollen grains they produce.  Each pollen grain is essential for the plants to pass on to other flowers of their own kind in order for fertilisation to occur and new progeny in the form of seeds for plants to perpetuate their species.  Flowers have built a very complex relationship between themselves and various pollinators, butterflies, bees, wasps and hoverflies to name the main contenders.  Pollen is food for some (our honeybees in particular) providing protein and essential minerals and nutrients for the larvae to grow healthy and strong, the flowers provide nectar, a sweet energy rich treat for some and an enticement and reward for the insect which gets laden with pollen to transfer to the next flower. 

Honeybees are very important in this process, each bee concentrates on a particular flower so only visiting flowers of the same species in successive trips and therefore only the right pollen is taken to the next flower visited.  Some is passed on and some the bees pack into their pollen baskets (on their hind legs), each species of pollen has a different colour so by watching what colour pollen they return to the hive with you can get an indication of what flowers they are harvesting.  By observing what flowers are in bloom you can also predict what they might be foraging on at each stage in the year.

This is my collection of pollens in the sample, collected about the first half of May, two shades of yellow/orange a pale green and a creamy/white.  A pollen colour chart can give an indication of pollen colour for the month and by making a microscope slide and looking under magnification, shape and form can be seen and further identification made.
Pollens mixed with alcohol ready for slided
Slide of each pollen type

Individual coffee bean shaped pollen grains
Pollen 1 - pale creamy/yellow and under the microscope looks very much like coffee grains.  Using colour, and knowing what is in flower and checking pollen ID features these are Bluebell, worked hard by the bees as it provides a very good nectar source as well as pollen.

Pollen 2 - khaki green and under magnification distinctly triangular with circular features at the corners, ID features suggest Rosaceae family, and as there is an apple tree at the apiary and the colour matches, so it is from our apple tree which will bear lots of apples hopefully at the end of the summer, if this wind hasn't ripped all the blossoms off!
Individual triangular pollen grains of apple blossom

Pollen 3 - colour, a dull orangey yellow, looking at the colour charts I might have put these last two the other way around, however under magnification (although my cheap none-too high tech microscope shows none to clear) definition is not that great, the small round, poorly defined grains I put to be Dandelion.
Small circular pollen grains -projections on grain surface not discernible in image

Pollen 4 - deeper orange/brown and under magnification the grains were sometimes rounded and some rounded/triangular which clearly seemed a feature of Gorse from the guide.  I may be wrong and there was possibly some contamination of this last sample with some other grains mixed in.  Gorse is one of the most important flowers for our bees on Islay it flowers very early in the year (flowers even right through the winter) and the bees will visit them if the weather is suitable to fly out, late January this year we had a 'warmer' dry few days and the bees were bringing back Gorse pollen.
Gorse (?) pollen grains

Such studies bring another level of understanding to the complex relationship between flower and pollinator.  Once the current restrictions abate and normality ensues (whenever that will be?) we will have our microscopes available to look at pollens in the Nature Centre and we will get a more high resolution camera to take better pictures of the samples than my bargain Aldi/Lidl purchase of a few years back doesn't do justice to!
Fiona MacGillivray