198 On the Species of the Genus Primula in Essex.
on hot days a dozen or more beetles, belonging to this species
or a very closely allied one, may generally be found in the
flowers of the Dandelion or Charlock, which, if taken and
shaken into one's hand, readily take wing and fly away. In
going down the tube of both forms of flower they have a
struggle to pass the anthers and the stigma ; and I have seen
both 1. and s. flowers containing beetles in which the sides of
the stigma were well covered with pollen, as if the insects
brushed against them. If it should be proved that the beetles
are the fertilizers of Primroses, Darwin's explanation will
merely have to be modified a little. The reciprocal cross-
fertilization of the flowers would be as easily accomplished in
this way as in any other, for the beetles in passing up and down
to the nectary would have precisely the same effect as a bee's
proboscis in conveying the pollen.45 The case stands as
follows:—There are three species of Primula closely allied,
and very similar in the structure of their flowers. We know
that two of them (Cowslips and Oxlips) are regularly fertilized
by bees, but the little beetles just mentioned so seldom
frequent these that after an examination of many thousands
of flowers I have come to the conclusion that the beetles
enter them rather by accident than by design; and, as it is
not known what insects fertilize Primroses, it seems at least
possible that these small beetles may be the active agents.
Although Mr. Darwin protected his Primroses from the
larger insects, these small beetles may have got unobserved
through his nets and effected their fertilization, thus
accounting for the vastly greater degree of fertility possessed
by Primroses over Cowslips under the same conditions.46
45 My cousin, Mr. R. W. Christy, who has observed the number of
beetles frequenting the flowers, suggested to me that Darwin's belief in
the Primrose being fertilized by nocturnal Lepidoptera is untenable, as
there are very few such insects abroad in the early spring when Primroses
habitually blossom.
46 This seems the more probable, as I suppose that in heterostyled
plants (especially the long-styled forms) fertilization is impossible, except
through the agency of insects.
[Darwin observed that when both were protected by a covering of gauze
the long-styled Primrose-plants produced more seed than the s.; and it