Chapter 10

Just outside the door here at my country studio, almost in touch of its threshold, year after year there blooms a large clump of milkweed (_Asclepias cornuta_), and, what with the fragrance of its purple pompons and the murmurous music of its bees, its fortnight of bloom is not permitted to be forgotten for a moment. Only a moment ago a whiff of more than usual redolence from the open window at which I am sitting reminded me that the flowers were even now in the heyday of their prime, and the loud droning music betokened that the bees were making the most of their opportunities.

Yielding to the temptation, I was soon standing in the midst of the plants. The purple fragrant umbels of bloom hung close about me on all sides, each flower, with its five generous horns of plenty, drained over and over again by the eager sipping swarm.

But the July sun is one thing to a bee and quite another thing to me. I have lingered long enough, however, to witness again the beautiful reciprocity, and to realize anew, with awe and reverence, how divinely well the milkweed and the bee understand each other. After a brief search among the blossom clusters I return to my seclusion with a few interesting specimens, which may serve as a text here at my desk by the open window.

Two months hence an occasional silky messenger will float away from the glistening clouds about the open milkweed pods, but who ever thanks the bees of June for them? The flower is but a bright anticipation--an expression of hope in the being of the parent plant. It has but one mission. All its fragrance, all its nectar, all its beauty of form and hue are but means towards the consummation of the eternal edict of creation--"Increase and multiply." To that end we owe all the infinite forms, designs, tints, decorations, perfumes, mechanisms, and other seemingly inexplicable attributes. Its threshold must bear its own peculiar welcome to its insect, or perhaps to its humming-bird friend, or counterpart; its nectaries must both tempt and reward his coming, and its petals assist his comfortable tarrying.

Next to the floral orchids, the mechanism of our milkweed blossom is perhaps the most complex and remarkable, and illustrates as perfectly as any of the orchid examples given in Darwin's noble work the absolute divine intention of the dependence of a plant species upon the visits of an insect.

Our milkweed flower is a deeply planned contrivance to insure such an end. It fills the air with enticing fragrance. Its nectaries are stored with sweets, and I fancy each opening bud keenly alert with conscious solicitude for its affinity. Though many other flowers manage imperfectly to perpetuate their kind in the default of insect intervention, the milkweed, like most of the orchids, is helpless and incapable of such resource. Inclose this budded umbel in tarlatan gauze and it will bloom days after its fellow-blooms have fallen, anticipating its consummation, but no pods will be seen upon this cluster.

What a singular decree has Nature declared with reference to the milkweed! She says, in plainest terms, "Your pollen must be removed on the leg of an insect, preferably a bee, or your kind shall perish from the face of the earth." And what is the deep-laid plan by which this end is assured? My specimens here on the desk will disclose it all.

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 _stigma_ is to be seen in the flower, the stigmatic surface which is to receive the pollen being concealed within five compartments, each of which is protected by a raised tent-like covering, cleft along its entire apex by a fine fissure (A). _Outside of each of these, and entirely separated from the stigma in the cavity_, lie the pollen masses within their pockets, each pair uniting at the rim below in V-shape, the union at the lower limit of the fissure.

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.

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.

* * * * *

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.

INDEX

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; Wilson's thrush; chewink, 32; fly-catcher; bluebird; oven-bird; cat-bird; phoebe, 40; bobolink; "reed-bird," 53; humming, 227.

Birds' nests: --Flimsy structure of the cuckoo's, 26; song-sparrow's, 30; oriole's swinging hammock; cobweb structure of the vireo's, 32; size of yellow-bird's; summer yellow-bird's beautiful home, 47; a four-story house, a possible fashion in featherdom, 51; pipit's, 35; wood-sparrow's, 37.

Bittersweet (_Celastrus scandens_), queer little harlequins on, 9; its scarlet-coated seeds, 88.

Blackburn, Mrs., quoted, 35.

Blair, Patrick, his claims concerning pollen, 111.

Blossom ceremonies, 119.

Blue-flag, its hidden anthers reached only by the bumblebee or large fly,129; manner of the bee's approach, 131.

Burroughs on wren-building, 17.

Butterflies: --Great yellow swallow-tail (_Papilio turnus_); red admiral (_Pyrameis Atlanta_); small yellow (_Philodice_); semicolon (_Grapta interrogationis_); comma (_Vanessa comma_), 153; orange; white (_Aphrodite_), 154; white cabbage (_Pontia oleracea_) 153.

_Cactus_, prickly-pear, its golden bower, 118.

_Collinsonia_, horse-balm, 136.

Caterpillars, 10, 14, 15, 62.

_Celastrus scandens_, bittersweet, 88.

_Chamælirium luteum_, devil's-bit, 133.

Chipmonk, 6.

Cicada, victim of the sand-hornet, 77; manner of depositing its eggs; period of transformation, 97; time of hatching, 100.

Cicindela, tiger-beetle, 68.

Clover, cause of failure of crop in Australia, 117.

Cobwebs: --A dusty prize; a two year's span, 7; a mixed assortment in, 8.

Cone-flower (_Rudbeckia hirta_), 138; embryo seeds; arrangement of the anthers, 139.

Cow black-bird, 27; his favorite perch; old dame's theory, 28; an unwelcome intruder, 30; a prowling foe, 31.

Cow-bird: --Ravenous young parasite, 31; a clamoring lubber, 37; "Black Douglas" of the bird-home, 38; selected victims, 39; distribution of its eggs; vicious habits, 40; egg-laying intervals; demoralizing conditions; American species an improvement, 41; survival of the fittest, 42; balance of power, 44; outwitted, 51; massing for migration, 52.

"Cow-spit," 80.

Cross-fertilization, 115, 122, 178, 189, 194.

"Cuckoo-spit," 80.

Cuckoos: --Poetic misnomer, 23; outrage on maternal affection; yellow-billed; black-billed; imagination versus facts, 25; bad workmanship of nest, 26; its stammering cry, 27; manner of depositing its eggs; handling the egg with her bill, 33; short period of incubation; voracious appetite of the young; aggressive selfishness, 34; the tragedy of the nest, 35; manner of disposing of its nest-mates, 36.

_Cypripedium acaule_, moccasin-flower; ladies'-slipper; Venus's-slipper, 205.

Darwin: --Process of anatomical evolution, 35; theory of cross-fertilization, 105; inspired insight, 115; his disciples, 116; experiments with pollen, 126; weakness of self-fertilizing flowers, 144; triumphant revelation, 171; reaffirming Sprengel's theory, 178; a chosen interpreter, 181; dependence on insects, 183; revealing the hidden treasure, 185; foretelling the manner of cross-fertilization, 189; description of the cross-fertilization, 209; bees as implied fertilizers, 212; truth of his belief, 220.

Darning-needle, dragon-fly (_Libellulidæ_), 156; his dainty morsel, 160.

Delpino, a follower of Darwin, 116.

_Desmodium_, its hospitable welcome, 118.

Devil's-bit (_Chamælirium luteum_), 133.

Digger wasp, its color and wire-like waist, 72; manner of working, 74; covering its tracks; opening the tomb, 76; living food for the young grub, 77; its remarkable carrying power, 78.

Dogbane (Apocynum), its fragrant, bell-shaped flowers, 236; trapping moths, 237.

Dogwood, 5.

Door-Step Neighbors: --Chronicle of a day, 58; disappearing holes, 59, 16; "ant-holes"; a danger signal; an unhealthy court, 61; a transformation, 62; an experiment; method of excavation, 63; a stalwart worker, 64; an uncouth nondescript; spider-like legs, 66; crawls on his back, 67; a tiny black wasp; a spider-catcher, 69; resting on her wings; inspecting her burrow, 70; manner of burying her prey; skilful workmanship, 71; a new-comer; her wire-like waist; digging her tunnel, 72; manner of working; sound of labor, 74; covering her tracks; opening the tomb, 76; fresh living food, 77; carrying seven times its weight; peculiar features of stone-piling, 78; color of the wasp, 79; the spume-bearer, 81; nomadic blossoms; a sack bearer, 83; winter quarters, 84.

Epeira, field spider, 8.

Epiphytes, air-plants, 181.

Evening primrose, its golden necklace, 118.

"Fertilization of Flowers," 116; wrong theory, 114.

Fertilization of orchids, 105, 183.

Flies: --Robber, 8; bluebottle, 8; harvest ichneumon, 45, 77, 96.

Foxes, wild gambols of, 6.

Froghopper. See Spume-bearer (_Aprophora_), 82.

Gärtner, recognizing the theory of cross-fertilization, 115.

Genesta, its reception of insects, 118.

Geranium, wild (_G. sylvaticum_), 112.

Gilbert, concerning cuckoo's eggs, 25.

"Gobs," 80.

Gray, Asa: --Demonstration concerning orchids, 184; surmise concerning the withdrawal of pollen, 188; orchid structure, 190.

Grew, Nehemias, discovery concerning pollen, 110; discoveries about pollen, 113; first step in progress, 116.

Habenaria flava: --Yellow-spiked, 203; _H. lacera_, ragged, 200; _H. orbicularis_, showy, 194, 199; _H. psycodes_, purple-fringed, 200; _H. mascula_, 189.

Heath, its distinguishing characteristics, 123.

_Hemiptera_, bugs with sucking beaks, 81.

Herbert: --A follower of Sprengel, 108; recognizing the principle of cross-fertilization, 115.

"Honey-dew Picnic": --Gathering of the clans, 153; a selected spot, 154; a motley assemblage, 155; an outlaw, 157; a finish fight, 158; funeral baked meats, 164; gathering his grist; the founder of the feast, 158.

Honey-guides, 112, 129.

Hornets: --Its heavy load, 9; on the watch, 15; "solitary," 17; queer home of, 18; great sand, 77; black paper, 161.

Horse-balm (_Collinsonia_), its singular shape, 136; manner of bee's approach to, 138.

Huber: --On insect slavery, 151; on the cultivation of the aphides, 166.

Insect Fertilization, 115.

Jack-in-the-Pulpit, detaining its guests, 119.

Jardine, Sir William, concerning cuckoo's eggs, 32.

Jenner, Dr., habits of the young cuckoo, 35.

Knight, Andrew: --On the divination of flowers, 108; theory of cross-fertilization, 115.

Köhlreuter: --Recognizing Sprengel's principles, 108; a botanical pioneer, 115.

Krunitz, on flower honey, 111.

Labiates, flowers with lips, 122.

Ladies'-tresses (_Spiranthes_), 218.

Larva: --Hornet, 16; "puss-moth," 76; psychid, 83.

Linnæus: --Settling the theory of fertilization, 110; puzzled as to the function of honey, 111; a second step, 116; imperfect knowledge of the orchid, 173.

Logan, concerning the cuckoo, 23.

Lubbock: --On the divination of flowers, 108; follower of Darwin, 116; on the cultivation of aphides, 166.

Martial Spirit of Vespa, 19.

_Membracis binotata_, insect with a sharp beak, a tree-hopper, 91.

Milkweed: --Its matchless hospitality; purple pompons; its five horns, 227; its one mission; the humming-bird its friend, 228; complex mechanism; enticing fragrance; removal of pollen on insects' legs, 229; four captives, 230; its honey trap; its tenacious grip, 233; an assortment of victims; cumbersome handicap, 234; a wholesale destroyer, 235.

Mint family, 122.

_Mnio-tiltidæ_, summer yellow-bird, 47.

Moccasin-flower (_Cypripedium acaule_), 205.

Moths: --Twilight; sphinx, 118, 190, 220; grape-vine, 160.

Mountain laurel: --Showers of pollen of; curious construction of flower of; withers if brought indoors, 124; character of the pollen, 125.

Mouse, motley collection of food of; mischief of, 7.

Müller, Hermann: --On the divination of flowers, 108; on defective observation, 114; the relations between the flower and insect, 116; on fertilization, 142

Nature's Equilibrium, 39.

Natural observation, 57.

Nomadic blossoms, 83.

Orchids: --Dependence on insects, 144; strange mechanical adaptation; sweet-pogonia; perfume suggesting raspberries, 145; intention of the blossom, 146; adaptation for insects, 147; its fragrance a perfumed whisper of welcome, 148; a contrast, 172; form of invitation, 173; insect complement, 174; Arethusa bulbosa, 175; theories concerning the conveyance of the pollen, 176; the most highly specialized form of flowers, 180; distinguished by its structure; American varieties not air-plants; form of flower, 181; elasticity of the pollen of the _Spectabilis_, 182; self-fertilizing, 183; American and exotic species, 184; Arethusa's fragrance, 185; its structure, 186; significant depth of nectar wells; conditions demanded of insects, 187; Gray's surmise, 188; sphinx-moth its only complement, 190; manner of carrying the pollen by sphinx-moth, 193; extracting the pollen with a pencil; length of the nectary, 196; purple-fringed, 198; ragged, 200; very exceptional provision, 201; yellow-spiked, 203; moccasin-flower; ladies'-slipper; Venus's-slipper; the color of, 205; distinctive character of, 206; practical experiment, 209; imprisonment of the bee; manner of its release, 210; rattlesnake-plantain, 213; Angræcum, its long nectary, 219; tongue of a sphinx-moth eleven inches long, 220; nectary thirteen inches long, 223.

"Origin of Species": --First important presentation of the theory of cross-fertilization, 105; tardy appreciation of the work, 115.

_Odynerus flavipes_, wren-wasp, 10.

Ovid, concerning hornets, 18.

Parallels in Nature, 152.

Platanthera, orchid group, 192.

Pliny, 23.

_Pogonia ophioglossoides_, sweet-pogonia, 145.

Polistes, brown wasp, 161.

Primrose, evening, 118.

Psychid: --A sack-bearer; drags its house with it; feeds on seed-pods, 83; winter quarters of silk, 84.

Queer Little Family: --Tree-hopper (_Membracis binotata_); a singular entertainment; graceful curves, 87; a branch in masquerade; queer thorns, 88; a sudden disappearance; animated thorns; like a covey of quails, 89; like "Bob White," 90; singular agility; queer anatomy; always ready for flight, 91; fondness for locust and oak-trees, simulating the color and character of the branches, 92; manner of sitting on the branches, 93; always headed towards the top; tiny tufts of cotton, 94; color and size of the tufts; a mere frothy shell; a riddle, 95; its relations, 96; an investigation, 97; its technique, 98; aërated cement; froth-house builder, 99; period of hatching, 100; a house for the winter; not a wanderer, 101.

Ragged Orchid (_H. lacera_), 200.

"Rattlesnake-plantain," 213.

_Rudbeckia hirta_, cone-flower, 138.

Sage (_Salvia officinalis_), strange curved stamen, 119; nature's arrangement, 112.

Salvia, its welcome to the bee, 117.

Self-fertilization, 141.

Sheep-spit, 80.

Showy orchid (_H. orbicularis_),194.

Snorting war-horse, 18.

Solitude, the pleasures of, 3.

"Solomon's ant," 152.

Spectabilis, orchid, 182; its favorite haunt, 195.