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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directly between the two viscid discs, which immediately cling closer than a brother, and as the foot is finally withdrawn, the pollen is pulled from its cell.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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An interesting incident, apropos of our embarrassed bee, was narrated to me by the late Alphonso Wood, the noted botanist. He had received by mail from California a small box containing a hundred or more dead bees, accompanied by a letter. The writer, an old bee-keeper, had experience, and desired enlightenment and advice. The letter stated that his bees were "dying by thousands from the attacks of a peculiar fungus." The ground around the hive was littered with the victims in all stages of helplessness, and the dead insects were found everywhere at greater distances scattered around his premises. It needed only a casual glance at the encumbered insects to see the nature of the malady. They were laden two or three pairs deep, as it were, with the pollen masses of a milkweed. The botanist wrote immediately to his anxious correspondent, informing him, and suggesting as a remedy the discovery and destruction of the mischievous plants, which must be thriving somewhere in his neighborhood. A subsequent letter conveyed the thanks of the bee-keeper, stating that the milkweeds-a whole field of them-had been found and destroyed, and the trouble had immediately ceased. I am not aware that Mr. Wood ever ascertained the particular species of milkweed in this case. It is not probable that our Eastern species need ever seriously threaten the apiary, though unquestionably large numbers of bees are annually destroyed by its excessive hospitality. I have repeatedly found honey-bees dead beneath the plants, and my cabinet shows a specimen of a large bumblebee which had succumbed to its pollen burden, its feet, and even the hairs upon its body, being fringed deep with the tiny clubs-one of the many specimens which I have discovered as the "grist in the mill" of that wise spider which usually spreads his catch-all beneath the milkweeds.
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Allied to the milkweed is another plant, the dogbane (Apocynum ), which has a similar trick of entrapping its insect friends. Its drooping, fragrant, bell-shaped white flowers and long slender pods will help to recall it. But its method of capture is somewhat similar to the milkweed. The anthers are divided by a V-shaped cavity, into which the insect's tongue is guided as it is withdrawn from the flower, and into which it often becomes so tightly wedged as to render escape impossible. I have found small moths dangling by the tongue, as seen in the illustration below.
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INDEX
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Agalena, house-spider, 7.
Alypia, grape-vine-moth, 160.
Andromeda (A. ligustrina),
singular greeting to the bee, 126;
interior arrangement of flower, 128;
release of the pollen, 129.
Angræcum, orchid of Madagascar, with nectary eleven inches long, 219.
Ants,
herding the aphides, 166;
a model honey-farm, 167.
"Ant-holes," 61.
Aphides, plant-lice,
founders of the feast, 165;
herded by ants, 167.
Apocynum, dogbane, 236.
Aprophora, spume-bearer, 82.
Arethusa bulbosa, orchid, 175.
Argiope, field spider, 8.
Aristolochias, 119.
Aristotle, 23.
Arum, wild:
-Position of the anthers, 141;
progressive stages of change, 142.
Asclepias cornuta, milkweed, 227.
Asilus, "robber-fly", 8.
Axell, a follower of Darwin, 116.
Bees:
-The drone of, 5;
a counterpart of clover; dependence of clover on, 117;
manner of approach, 121;
black-and-white banded, 126;
approach to the blue-flag, 131;
experiment with the bumblebee, 209;
his escape from the flower, 210;
manner of cross-fertilizing, 212;
manner of conveying the pollen, 218;
his difficulties with the milkweed flower, 233;
the cumbersome handicap, 234;
destroyed by the milkweed, 235.
Beetles (Cicindela), tiger, 68.
Birds:
-Swifts, 5;
robin, 5;
vireo, 5, 45;
indigo, 5;
chat, 5, 40;
oriole, 5, 32;
red-headed chippy; barn-swallow, 6, 28, 39, 40;
cuckoo, 23;
"kow-bird"; cow black-bird; bunting, 27;
song-sparrow, 30, 40;
Maryland yellow-throat, 28, 45;