Part 2
For it is quite true what Mary says. The little white seed-like thing glued on to the last looper's body is the egg of the wasp, and the stung and paralyzed but not killed measuring-worms are the food stored up by this extremely clever narrow-waisted mother for the wingless, footless, blind, almost helpless wasp grub, when it shall hatch from the egg. Down in the darkness of the cell, there will be a horrible tragedy. For days and weeks together the wasp grub will nibble away on the helpless loopers until all five are eaten alive! Then the grub will change to a winged wasp with strong sharp jaws with which she will dig her way up and out of the noisome prison and into the free air and sunlight of the marsh room. And she will then dig holes of her own, find and sting and store loopers, lay an egg on one, and close up the hole just as her mother did. Or at least all this would happen if we hadn't collected the hole. But it will happen in the other holes.
But why should the loopers be only paralyzed instead of killed? Isn't it plain that if killed they would only be decaying carrion by the time the wasp grub was ready to eat them, and young wasps must have fresh meat, not dead and decayed flesh. And if the loopers were simply put in alive, not paralyzed, wouldn't their violent squirming in the hole surely crush the delicate egg or the more delicate newly hatched wasp grub? Or wouldn't they simply dig their way with their heavy jaws out of the hole and away? Or, indeed, could the slender-bodied mother wasp carry and handle successfully a strong squirming looper over an inch long? The reason for the paralyzing of the worms is plain then. But how is this extraordinary condition brought about? And the answer to this, which Mary and I didn't discover for ourselves, but had to find out from the accounts of the men who did, like Fabre and others, reveals the most extraordinary thing that our wasps do. Most people think the wasps that live in communities or large families in big paper nests (the yellow-jackets and hornets) are the most interesting and most intelligent or clever of the wasps. But Mary and I do not think so. The solitary wasps do the most wonderful things, and of all they do, the paralyzing of the insects they store up as food for their young is the hardest to explain on any basis except that of wasp reasoning. But of course we don't have to explain it, which is fortunate for the high record of truth we are trying to establish in this book.
Fabre, the patient Frenchman, waited for years and years for a chance to see just how the Ammophila paralyzes her victims, and at last he saw and understood it. To understand the matter from Fabre's account of it, we must remember that the measuring-worm's body is made up of a series of rings or body segments, in each of which (except the very last) is a little nerve center or brain situated just under the skin on the under side of the body. And all this row of brains is connected by a slender nerve cord running along the middle line of the under side of the long body. Now Fabre saw that the wasp darted its sting into each looper, "once for all at the fifth or sixth segment of the victim." And when he pricked the stung worms with a needle in various parts of the body, he found, just as Mary did, that the needle could entirely pierce the middle of the body (which is where the fifth and sixth segments are), without causing any movement of the worm. "But prick even slightly a segment in front or behind and the caterpillar struggles with a violence proportioned to the distance from the poisoned segment."
Now what is the reason, asks Fabre, for the wasp's selecting this particular spot for stinging the worm, and he answers his own question as follows:
"The loopers have the following organization, counting the head as the first segment: Three pairs of true feet on rings two, three, and four; four pairs of membranous feet on rings seven, eight, nine, and ten, and a last similar pair set on the thirteenth and final ring; in all eight pairs of feet, the first seven making two marked groups--one of three, the other of four pairs. These two groups are divided by two segments without feet, which are the fifth and sixth.
"Now, to deprive the caterpillar of means of escape, and to render it motionless, will the Hymenopteron [that's the wasp] dart its sting into each of the eight rings provided with feet? Especially will it do so when the prey is small and weak? Certainly not: a single stab will suffice if given in a central spot, whence the torpor produced by the venomous droplet can spread gradually with as little delay as possible into the midst of those segments which bear feet. There can be no doubt which to choose for this single inoculation; it must be the fifth or sixth, which separate the two groups of locomotive rings. The point indicated by rational deduction is also the one adopted by instinct. Finally, let us add that the egg of the Ammophila is invariably laid on the paralyzed ring. There, and there alone, can the young larva bite without inducing dangerous contortions; where a needle prick has no effect, the bite of a grub will have none either, and the prey will remain immovable until the nursling has gained strength and can bite farther on without danger."
But some Ammophilas catch much larger caterpillars than the inch-long, slender, little loopers. Fabre found a wasp dragging to its nest a caterpillar weighing fifteen times the weight of the wasp. Does one stab suffice for such a giant caterpillar? Here is what Fabre saw: An Ammophila was noticed scratching in the ground around the crown of a plant. She was "pulling up little grass roots, and poking her head under the tiny clods which she raised up, and running hurriedly, now here, now there, round the thyme, visiting every crack which gave access under it; yet she was not digging a burrow, but hunting something hidden underground, as was shown by manoeuvres like those of a dog trying to get a rabbit out of its hole. And presently, disturbed by what was going on overhead and closely tracked by the Ammophila, a big gray worm made up his mind to quit his abode and come up to daylight. It is all over with him; the hunter is instantly on the spot, gripping the nape of his neck and holding on in spite of his contortions. Settled on the monster's back, the Ammophila bends her abdomen, and, methodically, deliberately--like a surgeon thoroughly familiar with the anatomy of his subject--plunges a lancet into the ventral surface of every segment, from the first to the last. Not one ring is omitted; with or without feet each is stabbed in due order from the front to the back."
This is what the patient, careful observer saw, with all the "leisure and ease required for an irreproachable observation." "The wasp acts," says Fabre, "with a precision of which science might be jealous; it knows what man but rarely knows; it is acquainted with the complex nervous system of its victim, and keeps repeated stabs for those with numerous ganglia. I said 'It knows; is acquainted'; what I ought to say is, 'It acts as if it did.' What it does is suggested to it; the creature obeys, impelled by instinct, without reasoning on what it does. But whence comes this sublime instinct? Can theories of atavism, of selection, of the struggle for life, interpret it reasonably?"
When I had finished reading this to Mary she looked up and said softly: "Of course I don't understand all this that he says about 'avatism and selection' and so on, but I think the wasp knows. Don't you?"
"Mary," I reply promptly, "the word is 'atavism,' not 'avatism,' please remember!"
"I hope I can," said Mary.
RED AND BLACK AGAINST WHITE
The meadow lark on the fence post behind my house is unusually voluble this uncertain morning; maybe he is getting his day's singing off before the sun shall hide, discomfited, behind the unrolling cloud furls. A solemn grackle, with yellow eyes and bronzed neck, stalks with cocking head in the wet green of the well-groomed front lawn; a whisking bevy of goldfinches, which chat to each other in high-pitched hurried phrases, disposes itself with much concern in the bare tree across the road, and swinging along overhead, a woodpecker cries its harsh greetings. But the life here on the street is tame and usual compared to that busy living and to those eventful happenings taking place in a remoter corner of the garden. There where the warm dust is figured with the dainty tracks of the quail hosts and the flower-flies hum their contentedest note; there in that half-artificial, half-wild covert of odorous vegetation, a life in miniature, with the excitement and stresses, the failures and successes and the inevitable comedies and tragedies of any world of life is going on, with the history of it all unrecorded.
Mary has just come to call on me, bringing an unkempt bouquet of Scotch broom from the garden. On these branches of broom are many conspicuous white spots. They are not flowers, for it is not broom flower time, and the flowers are yellow when their time does come. But these white spots, soft little cottony masses, like little pillows or cushions, and with regular tiny flutings along the top, have puzzled Mary, and she has come to ask me about them, for I am supposed to know all things. Well, luckily, I do happen to know about these, but I suggest that we go into the garden together and see if we can find out. The truth is, I am glad of an excuse to get away from this tiresome German book about _Entwicklungslehre_. And then, too, I want to look at things and talk with Mary.
Mary has such a fascinatingly serious way of doing things that aren't serious at all. She has got the curious notion lately that many little people live among the grasses, the grass people she calls them, and that that is the reason there are so many very little white flowers coming up in my lawn. My own notion had been that some rascally seedsman had sold me unclean grass seed, but Mary's notion that the grass people are planting and raising these little flowers for their own special delectation is, of course, a much wiser one. So when we walk on the lawn, we go very slowly, and I have to poke constantly among the grasses with my stick as we move along so that the little people may know we are coming and have time to scurry away from under our great boots.
When we got out to the row of brooms, we found many of the soft white cushions on all the bushes. But some of them were torn and dishevelled. And in these torn masses many tiny round particles could be seen. These little black specks are simply eggs, insect eggs, as I told Mary, and soon she had discovered among them some slightly larger but still very small red spots which were waving tiny black feet and feelers about. They were of course the baby insects just hatching from the eggs.
"Does the mother lay the eggs in these little white cushions and then go away and leave them?" asks Mary.
"No, she stays right by them," I answer.
"But where is she then? I can't--Yes I can too," cries Mary in great triumph. "Here she is at one end of the egg cushion. She is a part of it."
"Well, no, not exactly," I have to say. "It is part of _her_, or rather she spins the cushion, which is really a sac or soft box of white wax, in which to lay her eggs. Something the way the spiders do, you know. Only their egg box is made of silk and usually fastened to a fence rail or on the bark of a tree and left there. But some of the spiders, the large, swiftly running, black kinds that live under stones, carry the silken ball with the eggs inside about with them, fastened to the end of the body. Well, this cottony cushion scale insect--that's its right name--keeps its waxen sac of eggs fastened to it, but as the egg sac is much larger than the insect itself, it can't run about any more, but has to stay for all the rest of the time until it dies in the spot where it makes the sac. However, as it gets all the food it wants by sticking its slender little beak into the broom or other plant it is on and sucking up the fresh sap, it gets on very well."
"But what makes some of the egg cushions--how pretty they are, too!--so torn and pulled open," asks Mary, who has listened to my long speech very nicely. She often gets impatient when I lecture for too many minutes together.
"That is for you to find out," I say. "There is a dreadful thing going on here if you can only see it. But a rather good thing too. Good for the broom bushes anyway, and as they are _my_ broom bushes and I like their flowers, good for me."
Just then a very stubby, round-backed, quick little red beetle with black spots walked off a broom stem on to Mary's hand. She didn't scream, of course, nor even jerk her hand away. She may learn when she is older to be frightened when pretty, harmless, little lady-bird beetles walk on her. But now she likes all sorts of small animals, and is not afraid at all.
Mary is not at all slow to understand things, and when this hard-bodied little beetle, with a body like half a red-and-black pill, walked off the broom on to her hand, she guessed that he might have something to do with the torn-up egg cushions. So it didn't take her long to find another little beast like him actually nosing about in an egg sac and voraciously snapping up all the unfortunate tiny, red, black-legged baby scale insects. He ate the eggs, too, and seemed to take some bites at the mother insect herself, and then Mary found more of the lady-bird beetles, and still more. They were on all the broom bushes where the white cushions were. And so one of the dreadful tragedies going on in my garden was soon quite plain to Mary, and she was very sorry for the helpless white insects.
"Where did the red beetles come from?" she asked pretty soon.
"From Australia," I answered. "Or rather their great-great-grandparents did. These particular beetles were probably born right here in the garden, because a colony of them live here. But they couldn't if there were not some cottony cushion scale insects here too. For this particular kind of lady-bird beetle can't live on any other food--at least they don't--except this particular kind of scale insect and its eggs, which is surely a curious thing, isn't it?"
But Mary is so used to finding that the insects have extremely unusual and curious habits--that is, habits different from ours--that she doesn't get excited any more when I tell her about them. She does though when she finds them out for herself, which makes me wonder if I haven't wasted a good deal of time in my life giving lectures to students about things instead of always making them find out for themselves. And maybe I am wasting some more time now while I am writing!
"How did they come from Australia?" asks Mary. For she knows that Australia is several thousand miles away across the ocean from California, and lady-bird beetles do not swim. At least not from Australia to America. So I have to give Mary another informing lecture, and this is it:
"Years and years ago, there lived in some fragrant-leaved orange-trees in Australia some white cottony cushion insects whose life was untroubled by other cares than those of eating and of looking after the children. As each insect was fastened for life on the leaf or twig that supplied it with all the food it needed, which was simply an occasional drink of sap, and as the white insects always died before their children were born, neither of these cares was very harassing. On thousands of other similar fragrant-leaved orange-trees in Australia lived millions of other similar white insects. And for a long time this race of white insects enjoyed life. Those were happy days. But on a time there came into one of the trees a few small red beetles, who eagerly and persistently set about the awful business of eating the defenceless white insects. From this tree the red beetles, or the children of them, went to other trees where white insects lived, and with unrelenting rapacity and uncloyed appetite ate all the white insects they could find. And so in other trees; and finally, with years, the red beetles had invaded all of the thousands of fragrant-leaved orange-trees in Australia, and had eaten nearly all of the millions of white insects.
"One day a very small orange-tree was taken out of the ground in Australia and sent with many others across the ocean to California. On this small tree there were a few of the white insects. The little tree was planted again in California and soon put out many fresh fragrant leaves. The white insects were astonished and rejoiced that day after day went by without the appearance of any red beetles. The white insects increased in numbers; there were thousands of fragrant-leaved orange-trees in California, and in a few years there were millions of white insects in them. One morning a man stood among the trees and said, 'Confound these bugs; they'll ruin me; what shall I do?' and a man who knew said, 'Get some red beetles from Australia.' So this orange-grower, with some others, paid a man to go to Australia and collect some live red beetles. The collector went across the ocean, three weeks' steady steaming, and sent back a few of the voracious little beetles in a pill box. They were put into a tree in a California orange-orchard in which there were many cottony cushion scale insects. The red insects promptly began eating the white ones; and their children and grandchildren and great-grandchildren have kept up this eating ever since. And so the orange-growers never tire of telling how the red beetles (whose name is Vedalia) were brought from Australia to save them from ruin by the white insects (whose name is Icerya)."
Now there are not many cottony cushion scales left in California. A very promising colony of them seems to have sprung up in my Scotch broom bushes. But the red beetles have found their way there already, as Mary and I discovered to-day, and so we think that by the time the broom flowers come, there will be few white insects left in the bushes.
THE VENDETTA
This is the story of a fight. In the first story of this book, I said that Mary and I had seen a remarkable fight one evening at sundown on the slopes of the bare brown foothills west of the campus. It was not a battle of armies--we have seen that, too, in the little world we watch,--but a combat of gladiators, a struggle between two champions born and bred for fighting, and particularly for fighting each other. One champion was Eurypelma, the great, black, hairy, eight-legged, strong-fanged tarantula of California, and the other was Pepsis, a mighty wasp in dull-blue mail, with rusty-red wings and a poisonous javelin of a sting that might well frighten either you or me. Do you have any wasp in your neighborhood of the ferocity and strength and size of Pepsis? If not, you can hardly realize what a terrible creature she is. With her strong hard-cased body an inch and a half long, borne on powerful wings that expand fully three inches, and her long and strong needle-pointed sting that darts in and out like a flash and is always full of virulent poison, Pepsis is certainly queen of all the wasp amazons. But if that is so, no less is Eurypelma greatest, most dreadful, and fiercest, and hence king, of all the spiders in this country. In South America and perhaps elsewhere in the tropics, live the fierce bird-spiders with thick legs extending three inches or more on each side of their ugly hairy bodies. Eurypelma, the California tarantula, is not quite so large as that, nor does he stalk, pounce on and kill little birds as his South American cousin is said to do, but he is nevertheless a tremendous and fear-inspiring creature among the small beasties of field and meadow.
But not all Eurypelmas are so ferocious; or at least are not ferocious all the time. There are individual differences among them. Perhaps it is a matter of age or health. Anyway, I had a pet tarantula which I kept in an open jar in my room for several weeks, and I could handle him with impunity. He would sit gently on my hand, or walk deliberately up my arm, with his eight, fixed, shining, little reddish eyes staring hard at me, and his long seven-jointed hairy legs swinging gently and rhythmically along, without a sign of hesitation or excitement. His hair was almost gray and perhaps this hoariness and general sedateness betokened a ripe old age. But his great fangs were unblunted, his supply of poison undiminished, and his skill in striking and killing his prey still perfect, as often proved at his feeding times. He is quite the largest Eurypelma I have ever seen. He measures--for I still have his body, carefully stuffed, and fastened on a block with legs all spread out--five inches from tip to tip of opposite legs.
At the same time that I had this hoary old tarantula, I had another smaller, coal-black fellow who went into a perfect ecstasy of anger and ferocity every time any one came near him. He would stand on his hind legs and paw wildly with fore legs and palpi, and lunge forward fiercely at my inquisitive pencil. I found him originally in the middle of an entry into a classroom, holding at bay an entire excited class of art students armed with mahl-sticks and paint-brushes. The students were mostly women, and I was hailed as deliverer and greatest _dompteur_ of beasts when I scooped Eurypelma up in a bottle and walked off with him.
But this is not telling of the sundown fight that Mary and I saw together. We had been over to the sand-cut by the golf links, after mining-bees, and were coming home with a fine lot of their holes and some of the bees themselves, when Mary suddenly called to me to "see the nice tarantula."
Perhaps nice isn't the best word for him, but he certainly was an unusually imposing and fluffy-haired and fierce-looking brute of a tarantula. He had rather an owly way about him, as if he had come out from his hole too early and was dazed and half-blinded by the light. Tarantulas are night prowlers; they do all their hunting after dark, dig their holes and, indeed, carry on all the various businesses of their life in the night-time. The occasional one found walking about in daytime has made a mistake, someway, and he blunders around quite like an owl in the sunshine.
All of a sudden, while Mary and I were smiling at this too early bird of a tarantula, he went up on his hind legs in fighting attitude, and at the same instant down darted a great tarantula hawk, that is, a Pepsis wasp. Her armored body glinted cool and metallic in the red sunset light, and her great wings had a suggestive shining of dull fire about them. She checked her swoop just before reaching Eurypelma, and made a quick dart over him, and then a quick turn back, intending to catch the tarantula in the rear. But lethargic and owly as Eurypelma had been a moment before, he was now all alertness and agility. He had to be. He was defending his life. One full fair stab of the poisoned javelin, sheathed but ready at the tip of the flexible, blue-black body hovering over him, and it would be over with Eurypelma. And he knew it. Or perhaps he didn't. But he acted as if he did. He was going to do his best not to be stabbed; that was sure. And Pepsis was going to do her best to stab; that also was quickly certain.
At the same time Pepsis knew--or anyway acted as if she did--that to be struck by one or both of those terrible vertical, poison-filled fangs was sure death. It would be like a blow from a battle-axe, with the added horror of mortal poison poured into the wound.