Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/50

30 that various exotic species, both in this country and in their native homes, invariably fail to yield seed-capsules, when the flowers are fertilised with their own pollen.

From the observations already given, and from what will hereafter be shown with respect to Gymnadenia, Habenaria, and some other species, it is a safe generalisation that species with a short and not very narrow nectary are fertilised by bees and flies; whilst those with a much elongated nectary, or one having a very narrow entrance, are fertilised by butterflies or moths, these being provided with long and thin proboscides. We thus see that the structure of the flowers of Orchids and that of the insects which habitually visit them, are correlated in an interesting manner,—a fact which has been amply proved by Dr. H. Müller to hold good with many of the Orchideæ and other kinds of plants.

With respect to Orchis pyramidalis, which possesses, as we have seen, an elongated nectary, Mr. Bond was so kind as to send me a large number of Lepidoptera, out of which I selected twenty-three species, enumerated in the following list, with the pollinia of this Orchid, which can easily be recognised, attached to their proboscides.