pollen-masses and thus to fertilise them. I
have, also, reason to believe have, also, reason to believe 1859 1860 |
find from experiments 1861 1866 1869 1872 |
that humble-bees are
indispensable indispensable 1859 1860 | almost indispensable 1861 1866 1869 1872 |
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. ↑4 blocks not present in 1859 1860; present in 1861 1866 1869 1872 | I have also found that the visits of bees are necessary for the fertilisation of some kinds of clover: for instance, 20 heads of Dutch clover (Trifolium repens) yielded 2,290 seeds;
but 20 other heads protected from bees produced not one.
Again, 100 heads of red clover (T. pratense) produced
2,700 seeds, but the same number of protected heads produced not a single seed.
Humble-bees alone visit red clover, as other bees cannot reach the nectar.
It has been suggested that moths may serve to
fertilise the clovers; but I doubt this
in the case of the red clover, from their weight being apparently not
sufficient to depress the wing-petals.
|
Hence
I have very little doubt, I have very little doubt, 1859 1860 |
we may infer as highly probable 1861 1866 1869 1872 |
that that 1859 1860 1861 | that, 1866 1869 1872 |
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. Mr. H. 1859 1860 1861 | Col. 1866 1869 1872 |
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 Mr. Newman 1859 1860 1861 | Col. Newman 1866 1872 | Col.Newman 1869 |
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! |