We know now that flowers are indispensable to the greater number of anthophilous insects, and we know on the other hand, from the researches of Darwin, that insects are necessary to a great number of flowers, whose fertilization they assure,-particularly cross-fertilization, which is especially advantageous. Has this reciprocity of services a consequent reciprocal adaptation between the insects and the flowers which they frequent ? The adaptation of anthophilous insects to flowers is denied by no one. It is progressive, as we have shown in the beginning of this chapter, and reaches its maximum with the bee-flies, the butterflies, and the social bees.
The adaptation of flowers to the insect is more debated, and, indeed, more debatable. While Bonnier and Pl-ateau give it no weight, or very little weight, it seemed plain to Darwin, to Herman Miiller, to Perez, and above all to Lubbock,1 who has singularly exaggerated it. He says:
1 J. Lubbock, On the British Wild Flower Considered in Relation to Inseots, 1875.
Not only the form and the actual colors, the brilliant tints, the sweet perfume, and the honey of flowers have been developed little by little following an unconscious selection exercised by the insects, but even the arrangement of colors. . . . The form, the size, the position of the petals, the relative situation of the stamens and the pistil are disposed in relation to the visits of insects and in order to assure the great object (fertilization) which these visits are destined to produce.
This is not the place to press this question, and I will only say that it is possible that the emission of the nectar, the perfumes, and the floral colors result from an adaptation of the flowers to insects, but We can bring forward no proof. And I will add that, on the contrary, many of the floral structures seem to have this origin. Thus it is, for example, with the atrophy of the lower pollen sac in the Labiates with two stamens. To convince oneself of this, it suffices to watch a Mellif er visiting sage. With its head the insect pushes the little arm of the long connective stamen and submits it to violent friction. This friction acts upon the staminous tissues, and, as this has been done probably since the sages have existed, one can see that it has resulted in the gradual modulating of the pollen sacs on the little connective arm. In fact, the extremity of this arm presents often some traces of a p'olliniferous formation, and indeed in Salvia eretica these 'stamina! vestiges are still well developed and fertile.