Here are two bees, a fly, and a beetle, each hanging dead by its legs from a flower, an extreme sacrificial penalty, which is singularly frequent, but which was certainly not exacted nor contemplated in the design of the flower. A careful search among almost any good-sized cluster of milkweeds will show us many such prisoners. As in all flowers, the pollen of the milkweed blossom must come in contact with its stigma before fruition is possible. In this peculiar family of plants, however, the pollen is distinct in character, and closely suggests the orchids in its consistency and disposition. The yellow powdery substance with which we are all familiar in ordinary flowers is here absent, the pollen being collected in two club-shaped or, more properly, spatula-shaped masses, linked in pairs at their slender prolonged tips, each of which terminates in a sticky disc-shaped appendage united in V-shape below. These pollen masses are concealed in pockets (B) around the cylindrical centre of the flower, the discs only being exposed at the surface, at five equidistant points around its rim, where they lie in wait for the first unwary foot that shall touch them. A glance at the two views of this central portion of the flower, as it appears through my magnifying-glass-the honey-horns and sepals having been removed-will, I think, indicate its peculiar anatomy or mechanism. No
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With this more intimate knowledge of the floral anatomy, let us now visit our milkweed-plant and observe closely.
A bee alights upon the flower-the object of its visit being, of course, the sweets located in the five horn-shaped nectaries. In order to reach this nectar the insect must hang to the bulky blossom. Instantly, and almost of necessity, it would seem, one or more of the feet are seen to enter the upper opening of the fissure, and during the insect's movements are drawn through to the base. The foot is thus conducted directly between the two viscid discs, which immediately cling closer than a brother, and as the foot is finally withdrawn, the pollen is pulled from its cell. The member now released seeks a fresh hold, and the same result follows, the leg almost inevitably entering the fissure, and this time drawing in the pollen directly against the sticky stigmatic surface within. The five honey-horns have now been drained, and as our bee leaves the flower he is plainly detained by this too hearty "shake" or "grip" of his host, and quite commonly must exert a slight struggle to free himself. As the foot is thus forcibly torn away, the pollen mass is commonly scraped entirely off and retained within the fissure, or perhaps parts at the stalk, leaving the terminal disc clinging on the insect's leg. Occasionally, when more than one leg is entangled, the dangling blossom is tossed and swayed for several seconds by the vigorous pulling and buzzing, and a number of these temporary captives upon a single milkweed-plant are always to be seen.
Not unfrequently the mechanism so well adapted exceeds its functions and proves a veritable trap, as indicated in my specimens. I have found three dead bees thus entrapped in a single umbel of blossoms, having been exhausted in their struggles for escape; and a search among the flowers at any time will show the frequency of this fatality, the victims including gnats, flies, crane-flies, bugs, wasps, beetles, and small butterflies. In every instance this prisoner is found dangling by one or more legs, with the feet firmly held in the grip of the fissure.
Almost any bee which we may catch at random upon a milkweed gives perfect evidence of his surroundings, its toes being decorated with the tiny yellow tags, each successive flower giving and taking, exchanging compliments, as it were, with his fellows. Ordinarily this fringe can hardly prove more than an embarrassment; but we may frequently discern an individual here and there which for some reason has received more than his share of the milkweed's compliments. His legs are conspicuously fringed with the yellow tags. He rests with a discouraged air upon a neighboring leaf, while honey, and even wings, are seemingly forgotten in his efforts to scrape off the cumbersome handicap.
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