It must not be supposed from these several statements that insects strictly confine their visits to the same species.  They often visit other species when only a few plants of the same kind grow near together.  In a flower-garden containing some plants of Oenothera, the pollen of which can easily be recognised, I found not only single grains but masses of it within many flowers of Mimulus, Digitalis, Antirrhinum, and Linaria.  Other kinds of pollen were likewise detected in these same flowers.  A large number of the stigmas of a plant of Thyme, in which the anthers were completely aborted, were examined; and these stigmas, though scarcely larger than a split needle, were covered not only with pollen of Thyme brought from other plants by the bees, but with several other kinds of pollen.

That insects should visit the flowers of the same species as long as they can, is of great importance to the plant, as it favours the cross-fertilisation of distinct individuals of the same species; but no one will suppose that insects act in this manner for the good of the plant.  The cause probably lies in insects being thus enabled to work quicker; they have just learnt how to stand in the best position on the flower, and how far and in what direction to insert their proboscides. (11/6.  Since these remarks were written, I find that Hermann Muller has come to almost exactly the same conclusion with respect to the cause of insects frequenting as long as they can the flowers of the same species:  ‘Bienen Zeitung’ July 1876 page 182.) They act on the same principle as does an artificer who has to make half-a-dozen engines, and who saves time by making consecutively each wheel and part for all of them.  Insects, or at least bees, seem much influenced by habit in all their manifold operations; and we shall presently see that this holds good in their felonious practice of biting holes through the corolla.

It is a curious question how bees recognise the flowers of the same species.  That the coloured corolla is the chief guide cannot be doubted.  On a fine day, when hive-bees were incessantly visiting the little blue flowers of Lobelia erinus, I cut off all the petals of some, and only the lower striped petals of others, and these flowers were not once again sucked by the bees, although some actually crawled over them.  The removal of the two little upper petals alone made no difference in their visits.  Mr. J. Anderson likewise states that when he removed the corollas of the Calceolaria, bees never visited the flowers. (11/7.  ‘Gardeners’ Chronicle’ 1853 page 534.  Kurr cut off the nectaries from a large number of flowers of several species, and found that the greater number yielded seeds; but insects probably would not perceive the loss of the nectary until they had inserted their proboscides into the holes thus formed, and in doing so would fertilise the flowers.  He also removed the whole corolla from a considerable number of flowers, and these likewise