Monday, December 10, 2012

Charles Darwin and the Bumblebee (Humble Bee)

     This quote from Charles Darwin is applicable to present day bees.  Bees have a very weak immune system and are not very adaptive to environmental changes caused by us.  Global warming and the increased presence of agrochemical toxins are conditions many species of bees will not survive. Their extinction will effect others species dependent on their pollination.
     I think like many of us Charles had a special place in his heart for Bumble Bees or Humble Bees as they were known prior to World War I.  With the help of 5 or 6 of his children between the years 1854-1861 Charles made a number of recorded observations on the flight routes of male Humble Bees (Charles Darwin on the routes of male Humble Bees).  In the first edition of "On the Origin of the Species" by Charles Darwin (1859) he describes how essential Bumble Bees are for the pollination of plants and specifically the red clover (Trifolium pratense).  This he explains is because of it's unique ability to reach the nectar which eludes other bees. (Different pollinators for different plants)

     "Charles Darwin wrote of "humble-bees"... "plants and animals, most remote in the scale of nature, are bound together by a web of complex relations. [...] I have [...] reason to believe that humble-bees are indispensable to the fertilisation of the heartsease (Viola tricolor), for other bees do not visit this flower. From experiments which I have tried, I have found that the visits of bees, if not indispensable, are at least highly beneficial to the fertilisation of our clovers; but humble-bees alone visit the common red clover (Trifolium pratense), as other bees cannot reach the nectar. Hence I have very little doubt, that if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear. The number of humble-bees in any district depends in a great degree on the number of field-mice, which destroy their combs and nests; and Mr. H. Newman, who has long attended to the habits of humble-bees, believes that 'more than two thirds of them are thus destroyed all over England.' Now the number of mice is largely dependent, as every one knows, on the number of cats; and Mr. Newman says, 'Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice.' Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!" (from Chapter 3 "On the Origin of the Species").
     A logical extension made in jest by Thomas Henry Huxley (Huxley, 1892) was " that old maids keep cats, and by unknown others to include the concepts that the economy of the British Empire
was based on roast beef eaten by its soldiers, and cattle rely on clover, so as to conclude that the prosperity of the British Empire was thus dependant on its population of old maids." (Charles Darwin, Humble Bees, Clover and Cats).
  Bombus pascuorum (Common Carder-bee) on red clover

     As most bumblebees are ground dwellers their existence depends upon the population of nest destroying mice whose population depends on the subsequent population of predatory cats.  Therefore, the greater the population of cats the greater the number of bumblebees and the greater the pollination of red clover.  We must also consider the negative effect of cat predation on birds, amphibians and reptiles.  This is why an ecosystem functioning in equilibrium (balanced populations) is so important.
     In May of 1858 with the aid of a beekeeper Darwin carried out studies on honey bee cell building at his home in Kent, England.  "For people to accept his theory of evolution by natural selection Darwin knew that he had to explain how the hexagonal cells found in the wax of the beehive were fortified by natural processes.  As a result of his observations he concluded that the hexagonal shape is produced as a result of spherical cells touching each other and the bees using the minimum amount of wax possible.  The experiments are described in "On the Origin of the Species".

     The family home of Charles Darwin is wonderfully preserved in Kent and is much the same as it was in the 19th century when he and his children carried out their observations of both the honey and humble bee.

     Due to habitat loss and the use of agrochemicals many species of Humble Bees are endangered.  In Britain the Bumble Bee Conservation Trust is working to save the Humble Bees.  In North American join Bumble Bee Watch to help endangered species of Humble Bees.

Left Bombus Mixtus (Male) and right Bomus Caliginosus or Bombus Vosnesenskii on a sunflower at Cottonwood Garden

My favorite an Orange Rumped Humble Bee (Bombus melanopygus) enjoying a cranesbill geranium at Cottonwood Garden

Another Humble Bee beutifying Cottonwood Garden

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