an exactly
intermediate condition, or, as he expresses it, are more or less
dioeciously polygamous.

Let us now turn to the nectar-feeding insects; we may suppose the
plant of which we have been slowly increasing the nectar by continued
selection, to be a common plant; and that certain insects depended in
main part on its nectar for food. I could give many facts showing how
anxious bees are to save time: for instance, their habit of cutting
holes and sucking the nectar at the bases of certain flowers, which with
a very little more trouble they can enter by the mouth. Bearing such
facts in mind, it may be believed that under certain circumstances
individual differences in the curvature or length of the proboscis,
etc., too slight to be appreciated by us, might profit a bee or other
insect, so that certain individuals would be able to obtain their
food more quickly than others; and thus the communities to which they
belonged would flourish and throw off many swarms inheriting the same
peculiarities. The tubes of the corolla of the common red or incarnate
clovers (Trifolium pratense and incarnatum) do not on a hasty glance
appear to differ in length; yet the hive-bee can easily suck the nectar
out of the incarnate clover, but not out of the common red clover, which
is visited by humble-bees alone; so that whole fields of the red clover
offer in vain an abundant supply of precious nectar to the hive-bee.
That this nectar is much liked by the hive-bee is certain; for I have
repeatedly seen, but only in the autumn, many hive-bees sucking the
flowers through holes bitten in the base of the tube by humble bees.
The difference in the length of the corolla in the two kinds of clover,
which determines the visits of the hive-bee, must be very trifling; for
I have been assured that when red clover has been mown, the flowers of
the second crop are somewhat smaller, and that these are visited by many
hive-bees. I do not know whether this statement is accurate; nor whether
another published statement can be trusted, namely, that the Ligurian
bee, which is generally considered a mere variety of the common
hive-bee, and which freely crosses with it, is able to reach and suck
the nectar of the red clover. Thus, in a country where this kind of
clover abounded, it might be a great advantage to the hive-bee to have a
slightly longer or differently constructed proboscis. On the other hand,
as the fertility of this clover absolutely depends on