Selective Discrimination of Insects

Abstract

THE remarks of Sir John Lubbock in a late lecture on the relation of insects and flowers leads to the inference that in his opinion the brilliancy of colour rather than the odour is the attraction. My observations lead me to suppose that it is not the colour, but the particular odour of each variety or species of flower which induces the visit. With great interest, not unmixed with curiosity, I have observed (my attention was at first casually excited) that bees particularly, and also butterflies, visit a distinct variety and for the time confine their attention to it, settling on and sucking the honey of that variety only; e.g., a bee settling on a scarlet geranium will not go from it to another species or variety, but gives its attention to the particular variety only, irrespective of colour, whether scarlet, pink, or white, never going from a scarlet geranium to another scarlet flower, even if in contact. Whatever the species of flower, it is the same—pelargoniums, petunias, heliotropes, lilies, &c. The visit is from pelargonium to pelargonium, not from pelargonium to geranium (both cranes bills), and from lily to lily, irrespective of colour. I never remarked a bee go from a lily to an amaryllis, or the reverse. The object of this distinctive selection appears to be fertilisation. The indiscriminate admixture of the pollens of distinct varieties would probably frustrate the ends of nature and lead to monstrosities or barrenness. What would be the effect of the admixture on its own stores is a distinct question. So far as the insect is concerned, doubtless the fact has relation to its own economy. Whatever be the reason, there appears to be the harmonious adjustment of two facts under the relations of one law. If the colour, and not the odour, was the attraction, the visits would be indiscriminately made to all flowers of a brilliant hue. The observation of the lecturer as to flies being attracted by stinking plants or carrion seems to prove the fact suggested. Flies settle indiscriminately on all putrefactions, and will go immediately from a flower to offal or from offal to a flower. With bees and butterflies there is certainly a discriminative selection guided by odour; I have also remarked that some flowers are rarely, if ever, visited by bees.