In these cases the
bees knew the position of each plant in the garden perfectly well, as we
may infer by the directness of their flight; so that they were guided by
experience and memory. But how did they discover at first that the above
varieties with differently coloured flowers belonged to the same
species? Improbable as it may appear, they seem, at least sometimes, to
recognise plants even from a distance by their general aspect, in the
same manner as we should do. On three occasions I observed humble-bees
flying in a perfectly straight line from a tall larkspur (Delphinium)
which was in full flower to another plant of the same species at the
distance of fifteen yards which had not as yet a single flower open, and
on which the buds showed only a faint tinge of blue. Here neither odour
nor the memory of former visits could have come into play, and the tinge
of blue was so faint that it could hardly have served as a guide. (11/8.
A fact mentioned by Hermann Muller 'Die Befruchtung' etc. page 347,
shows that bees possess acute powers of vision and discrimination; for
those engaged in collecting pollen from Primula elatior invariably
passed by the flowers of the long-styled form, in which the anthers are
seated low down in the tubular corolla. Yet the difference in aspect
between the long-styled and short-styled forms is extremely slight.)
The conspicuousness of the corolla does not suffice to induce repeated
visits from insects, unless nectar is at the same time secreted,
together perhaps with some odour emitted.
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