|A beautiful Humble bee in my garden|
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 the following excerpt from "On the Origin of the Species" Darwin refers to the bumblebee as the humble-bee which was the original and common term for the bumblebee prior to World War I. I think I prefer humble bee.
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!"