Bug­man’s guide to com­mon pol­li­na­tors


The ba­sic prin­ci­ples of pol­li­na­tion are eas­ily un­der­stood: grab some pollen grains from the male parts of a flower (the an­ther) and some­how de­posit those on the top of the fe­male re­pro­duc­tive cen­tre (the stigma). Once a pollen grain sticks to the stigma it pro­duces a long pollen tube down the length of the style un­til it reaches the fe­male ga­me­to­phytes, where fer­til­i­sa­tion takes place.

You can make the story as com­pli­cated as you like, but the up­shot of this sys­tem is that fer­til­i­sa­tion of flow­ers results in ge­net­i­cally di­verse off­spring, mean­ing there will be vari­abil­i­ties in the plants that emerge from the seeds.

Pol­li­na­tion, then, is the way in which the pollen grains are de­liv­ered to the stigma and style. About 20 per cent of plants rely on wind and wa­ter to do that job and some 80 per cent of all plant species sim­ply grab the ser­vices of a pol­li­na­tor from the an­i­mal king­dom. We’re talk­ing birds and lizards, small pri­mates, ro­dents, bats and a whole line-up of bugs. And, as you guessed, it’s the in­ver­te­brates (es­pe­cially in­sects) that re­ally do a stand-out job here.

To at­tract the right kind of pol­li­na­tor, a plant has to have one or more tricks in its arse­nal. A colour which in­sects can see is handy. Blue or white (and all the shades in be­tween) are the best, as in­sects’ eyes ap­pear to be pretty poor at de­tect­ing the orange and red spec­tral ranges.

A good smell plays right into the an­ten­nae too. Th­ese long feel­ers are very sen­si­tive or­gans that can de­tect a few mol­e­cules of the right chem­i­cal and then ex­cite and guide the owner.

A nicely shaped flower can be at­trac­tive to an in­sect: there are fab­u­lous ex­am­ples of bee orchid flow­ers look­ing like a fe­male bee, which could be mounted by an alert male bee… Sorry mate!

And then there is the re­ward for the pol­li­na­tor – quick sus­te­nance, a de­cent dose of fruc­tose (en­ergy) and a sweet nectar that forms a build­ing block for mak­ing honey.

Of course, the pollen is chock­full of pro­tein that is use­ful for grow­ing new in­sect bod­ies. Some pol­li­na­tors are re­ally only in­ter­ested in pollen to stock the nurs­ery for their lar­vae to eat.

The hon­ey­bee ( Apis mel­lif­era) is by far the world’s most im­por­tant pol­li­na­tor of hu­man food crops – about one-third of our food has had some in­put from th­ese in­sects. Their amaz­ing work in­volves not just col­lect­ing and dis­tribut­ing pollen, but also turn­ing nectar into nu­tri­tious and medic­i­nal honey.

Why is honey so good for us and how do th­ese clever bees pro- duce this mir­a­cle ma­te­rial? In this case the hon­ours must go to the plants, dear gar­dener. Nectar is the ‘‘re­ward’’ plants make for the pol­li­na­tor’s ser­vices. Imag­ine what would hap­pen if a pol­li­na­tor finds its re­ward spoilt, smelling of fun­gal rot and crawl­ing with germy slime? I reckon the bee (and other pol­li­na­tors for that mat­ter) would soon give the in­com­pe­tent plant species a wide berth. This, of course, jeop­ar­dises the plant’s long-term fu­ture on this planet. To pre­vent the nectar from spoil­ing, plants cram it full of an­tibac­te­rial, anti-fun­gal and anti-mi­cro­bial sub­stances to keep it in fab­u­lous con­di­tion. All the bee has to do is gather it and turn it into honey. Shows you the im­por­tance of us­ing top-notch in­gre­di­ents!


Small gar­den bum­ble­bee, Bom­bus hor­to­rum

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