Insect Pollination

Updated: 1st March 2021

comma butterfly foraging on white flowers of Old Man's Beard - wild clematisComma butterfly


Insect pollination is also known as ‘entomophily’, which describes the pollination process whereby pollen is transferred from one flower to another by insects.


Insects are vital not only to the ecosystem, but also to global food supply for humans.  I have already written about bee pollination here.


Insect pollinators and pollination

Insect pollinators include:

  • bees
  • butterflies
  • wasps
  • moths
  • many various flies, such as hover flies
  • many various beetles.


How do insects pollinate flowers?


When visiting flowers, pollen sticks on to the body and legs of the insect.  The pollen is then transferred from the male parts of a flower to female parts, enabling pollination to take place.  Read more about the process of pollination.  

How do plants attract pollinating insects?

Plants have developed pollination syndromes to attract their ideal pollinators.  Depending on insect species (or indeed bird or animal pollinators - bats and hummingbirds, for example, are known to pollinate flowers), plants have various characteristics that will attract the target pollinator.  They are known as pollination syndromes.  These may include:

In my page about flower pollination, you can read more about how flowers are adapted to attract their ideal pollinators (pollination syndromes).

How Much Is Insect Pollination Worth?

hover fly and bumble bee on thistleHover fly and bumble bee on thistle

Attempts have been made to put a financial value on insect pollination.  However, ascribing a value is not easy.  Various research reports have been published with findings as follows:


  • 2012 study:  Jordan et al (1)
    "Economic Dependence and Vulnerability of United States Agricultural Sector on Insect-Mediated Pollination Service":
    Finds:

"....economic dependence of United States crops on insect-mediated pollination service at the county level and update existing coefficients of insect dependence of sample crops when possible. Economic value dependent on pollination service totals 34.0 billion USD in 2012. "

  • 2009 study:  Gallai et al (2)
    "Economic valuation of the vulnerability of world agriculture confronted to pollinator decline"

"The total economic value of pollination worldwide amounted to €153 billion, which represented 9.5% of the value of the world agricultural production used for human food in 2005."


Which insects are pollinating food crops, flowers and plants?

Honey (left) and hover fly (right) foraging on a pink Japanese anemone flower.A honey bee (left) and a hover fly (right) forage on a Japanese anemone flower.

Many insects play a role in pollinating crops, but also flowers, trees, shrubs and hedgerows.  Bees are the mostly widely understood pollinators, and honey bees have long received recognition for the pollination service they provide.  Read more about honey bee pollination.

However, increasingly, wild bees are being studied, and some species such as leafcutters are now known to be very efficient pollinators of alfalfa, mason bee species are helpful in orchards, whilst bumble bees are valued for their ability to increase tomato yields.  Still, the extent of the contribution from other insects is still not fully understood.

“…in Europe, a region better studied than most, about 250 plant species are grown as crops. Of these, about 150 are thought to be insect pollinated, but for most we do not know which insects pollinate them, or whether yields are being limited by inadequate pollination".  -  “Bumblebees Behaviour and Ecology” by Professor Dave Goulson, citing Corbet et al 1991 & Williams 1995. 



wasp on a raspberry flowerWasp on a raspberry flower


The Status And Decline of Insect Pollinators: Some Random Statistics


In Europe:
- It is estimated that 84% of EU crops (valued at £12.6 billion) and 80% of wildflowers rely on insect pollination. (source: Buglife)
- Across Europe 38% of bee and hoverfly species are in decline, and only 12% are increasing. (source: Buglife)
- 24% of Europe's bumblebees are believed to be facing extinction according to one report.


In the USA:
- 57 species of bees are on Red List – these are species that are seriously endangered or believed extinct. (Source: Xerces)
- 58 butterflies & moths are also on the US Red List. (Source: Xerces).


In the UK:

- Two thirds of UK moth species are in long term decline. (source: Buglife)
- “Lost” (possibly extinct) insect species include (among others): Bordered gothic moth (Heliophobus reticulata marginosa); Orange upperwing moth (Jodia croceago); Brighton wainscot moth (Oria musculosa) (source: Buglife)
- Over 75% of the 59 UK butterflies are declining and 5 species have become extinct. (source: Butterfly Conservation)
- 3 species of bumblebee have become extinct, and of the remaining 24 species, 2 are critically endangered, and 10 are in very serious decline. This includes 5 species that were common in the 1980s. (source: Bumblebee Conservation Trust).


Helping Insect Pollinators

  • Increase habitat and food for insect pollinators.
  • Cut out the insecticides, especially in gardens and public planting schemes.
  • By helping bees we are likely, by default, to help other pollinators - here are 10 tips.


Graphic noting that before using insecticides, it's worth remembering that 999 insect species out of every 1000 is harmless or beneficial.

References

(1)  Economic Dependence and Vulnerability of United States Agricultural Sector on Insect-Mediated Pollination Service;  Environmental Science & Technology 2021 55 (4), 2243-2253; DOI: 10.1021/acs.est.0c04786.

(2) Economic valuation of the vulnerability of world agriculture confronted to pollinator decline; Gallai, Nicola & Salles, Jean-Michel & Settele, Josef & Vaissière, Bernard. (2009). . Ecological Economics. 68. 810-821. 10.1016/j.ecolecon.2008.06.014. 








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