When this is over, the female beetle has accomplished her chief task, she will not live long. further care,[ 49 ]for the eggs she does not bear, protection seems superfluous and of course she cannot incubate them; for beetles do not have warm blood, like the birds. She just makes sure that the eggs don’t go too deep in the water, so that they can get enough sun heat.
Within 14 days the water is now teeming with tiny translucent larvae; the shape is not clearly distinguishable, but if you take good care of them with fine pieces of protein or meat fibres, they grow surprisingly fast. In about five days they are an inch long; they then get a new skin, again a day or so later they are already twice as long and molt again, up to three or four times.
Their appetite is surprisingly strong; but however carefully you feed them, their numbers are continually diminishing; probably the strong devour the weak, so that in the end not much remains.
They are therefore strongly developed. Their shape can now be clearly seen in the water; you will see animals such as you may have already caught at the same time as your adult beetle. They can hardly be compared in any way with the brimmed water beetle. (See fig. page 43 ).
Comb Salamander or Greater Newt. The male above, showing off for the female. In the middle a three-spined stickleback in the beautiful plumage.
Comb Salamander or Greater Newt. The male above, showing off for the female. In the middle a three-spined stickleback in the beautiful plumage.
We are dealing here with two forms of the same animal, almost as different from each other as the caterpillar of its butterfly.
In gluttony, however, the larva and the beetle are not inferior to each other, nor in combativeness. In this, beetles and butterflies differ as the crow flies.
The adult larva seizes with its formidable jaw pincers everything that comes within its reach, whether it be a frog larva, a stickleback, a salamander or a water snail; he is not afraid of a young pike. Big or small, dead or alive—everything is to his liking. He has no mouth; and this was also unnecessary,[ 50 ]for he sucks out his prey with the same pincers with which he seizes and kills it.
These suction hooks are hollow and have an opening close to the sharp point, from which a tube enters on both sides; these tubes can be seen quite well with the naked eye, they still unite in the head of the larva, and together form a wider tube, which is visible throughout the body.
In their favored position, head down, body curved forward, the six disproportionately long legs spread wide, they hang with the abdomen on the surface. Two pipes, air tubes, surrounded by hairs, can be distinguished there. So they hang like dead, lurking on the surface; until an unsuspecting fish or salamander comes within reach of paws or suckers. The salamander screeches loudly when he feels himself gripped by his mortal enemy. He struggles for a long time, but if you don’t deliver him quickly from his jumper, he’s done with it. He may dive, leap out of the water, dart in the water at lightning speed—he loses his leech no more than the hare that has been pounced by a weasel.
However, the time will come for this monster too, when his appetite diminishes, when he becomes sluggish and listless. It is now fully grown, and twice as long as the beetle from whose eggs it spawned.
If you have been able to raise them this far yourself, or, which is much easier, have scooped up a number of adult larvae, it is not much trouble to trace the metamorphosis.
In a goldfish bowl, place a stone that extends from the bottom to just below the surface of the water, and on top of it a piece of thick turf.
One morning the larvae have disappeared from the bowl.[ 51 ]If you carefully examine a part of the sod a week later, you will probably find one or more cavities, the size of a thimble, and in them a white or yellow doll. It differs in many respects from a butterfly doll, which you have certainly seen; especially because the parts of the future beetle are very clearly distinguishable.
Pupa of Dytiscus marginalis.
Pupa of Dytiscus marginalis.
After about three weeks, the doll skin tears open and the complete beetle emerges from it. Or rather does not appear yet, he is not yet visible, his chitin skin is still soft as wax and almost as yellow; his legs still too weak to row or crawl, his wings not yet dry enough.
In two or three days he has turned dark green in color and he feels strong enough to clear the earth that separates him from the water and find a living in his element.
That’s exactly what happens in the ditch. If he is not surprised at the last moment by a water rat or a mole, which comes to build his drinking passage at the ditch, he will soon be as skilled at grabbing his prey, at swimming, diving or flying, as his congeners. which have emerged much earlier; he needs no lesson from them; he does, however, become smarter and more dexterous as he goes on. Its youthful age is for the initiated in the secrets of a mud ditch, only recognizable by its lighter underside and the particularly strongly shiny elytra.
And the reproduction of the pitch black? “It won’t be that much of a difference,” you say, perhaps, as well as I used to. “Lay eggs, hatch larvae, molt, grow and molt again, then pupate and hatch,—that song[ 52 ]we already know by heart!” Exactly, but you might as well say that the life of all people is about the same; be born in this year, child, youth or girl, adult, then grow old and die, finally, in that year; so it went Napoleon and so it went Rembrandt, but with a difference, isn’t it? Indeed, if there was not much more to remark in the history of man or of nature, it was really not worth the trouble to study general, national or natural history.
Just as the life of all men is not equal, neither and much less is it the case with two species of animals, though both are water beetles. Once you ‘ve kept a pair of pitch-blacks in a bowl or aquarium, I’ll bet you’ll see to it every year not to be without them. Whether it is worth raising beetles with beetles, our Hydrophilus shows quite a bit more. He does not content himself, like the rimmed, to attach his eggs here or there to an aquatic plant, without further concern.
If you see the female of Hydrophilus swimming from time to time in April or May with leaves of duckweed, with green threads, or with a larger leaf of some aquatic plant, then an attractive activity will soon begin, which can only be done with one other water beetle. has been noticed .
It does just as well in a bowl of water as in the wide ditch. Don’t miss the opportunity to see a beetle underwater build a nest for its eggs and its young, a nest at least as artfully and purposefully arranged as that of a finch or oriole.
A nest under water? Yes, what else could it be called? Take a closer look at what the[ 53 ]beetle there with that blade performs; but do not disturb him; if you touch him, he stops, and then it depends on chance whether you will be right there when he starts again.
Look, the female lays on her back under that pondweed leaf, close to the surface, she constantly moves the abdomen back and forth; there she turns the leaf over and over: white threads are stretched across it transversely: now she takes it on the belly again, thread by thread emerges from four tubes at the abdomen; the two largest tubes are clearly visible during spinning and weaving.
Opened nest of Hydrophilus
Opened nest of Hydrophilus
signed after C. Mulder.
In half an hour the beetle has woven a apron, which it presses tightly against the sides of the body, over the raised keel, giving the apron a slight curve; the front legs are on the apron, the middle and hind legs below; thus the beetle rests for a few moments.
But there is haste to the work; she pushes off the apron with effort from all paws, grabs it with the forelegs or the jaws, and maneuvers until the cloth lies neatly on the back of her back; now the beetle turns again and begins again. Again a apron is ready in three quarters of an hour, but it has been spun together under the hand with the piece of cloth on the back; thus a skirt was created; this is closed from below, and there the beetle is now halfway in a whitish bag.
That seems to be the end, because there is no movement[ 54 ]more to detect; yes, it is as if the abdomen is extended extremely slowly, the longer and further, the front of the bag. And so it is; but you can only understand what happened afterwards; then it becomes clear why the beetle sat so still: it has laid fifty eggs at the bottom of the bag, in rows next to and on top of each other, but first she has covered the bottom with a layer of silk. (See fig. page 49 ).
Finishing the mast.
Finishing the mast.
(Seen on top of the water, so only the abdomen is visible).
Now the abdomen has come almost entirely out of the nest, and the beetle hastens to weave a flat cover over it; across, across, as if it were warp and weft, the threads pass over each other; This has to be done quickly, otherwise water might get in.
Larvae of the spinning water beetle with stickleback.
Larvae of the spinning water beetle with stickleback.
( To nature ).
More than once I have read that naturalists have remarked how the male supports the female in this; he keeps the nest in good condition, so that the female has only to weave; I saw it[ 57 ]never, but once did I see the male constantly swimming around the nest-building female, perhaps, to keep watch; once or twice I saw him sitting on the nest while the female was busy; I then asked someone who could know what that meant, and was answered: “It is to sustain the light nest until it is ready.”
The top half of the nest has filled the beetle with light tissue,—the eggs lie below; there is not much chance of it turning over, if it will soon start to float. It is also waterproof, and there is air and food in it for the young larvae.
However, the beetle has not yet completed its task to its liking. In strong winds the hulk could still perish; she will put up a mast; if the boat sometimes hits side, the tacky mast will touch the water, lean on it, and then straighten up again when the gust is over. (See Fig. page 11 and page 50. )
She spins that mast in an erect position, with her head down, and she lays the threads against each other lengthwise; each next one a bit longer than the previous one, so the mast can be a few centimeters long. Here too some have seen the male help; when the mast has become so high that the female’s abdomen can no longer reach it, the male presses the nest under by his weight.
If you notice anything special, write it down. Not all pitch blacks build in the same way. I haven’t had the luck ever to see it; I did notice in this spring that the female is best off alone. She aims halfway out of the water with the greatest of ease and spins the top of the mast with her brush-like spinning tubes. I made the attached drawing while the animal was busy.[ 58 ]
Once the female has begun to lay eggs, feel free to move the nest, or take it in your hand with the beetle next to it, to observe better. The animal can no longer be disturbed, and even continues laying eggs or making the lid on your hand, outside the water.
Just put it back in the water; see how the animal revolves around the nest, adds, adjusts or supplements here and there—and mark the date of the egg-laying. Ten days later you have to look at the nest from time to time; sometimes the larvae start to live in the nest. It can do no harm, at least if you have more than one nest, to carefully stick or cut a piece from the deck of the boat; then you can also see the change and the color change that takes place within it.
Within 14 days all the larvae have hatched, they eat silk and egg shells on the first day, but the next day their murder journey through the water in your bowls begins; then there is no snail, no worm safe from their jaws; they grow astonishingly fast and become larvae, so ugly, so creepy, that I, and many with me, can’t handle them without a little shiver of disgust, and we’re not so dirty or timid about insect-grabbing otherwise.
The larva of the rimmed is a monster, but–it can be seen; but that of the spinning water-beetle is a thick, soft, black, strongly wrinkled worm, which keeps itself dead when you fish it up, and which lies before you folded in half like a flabby skinned gut; you want to throw the filthy thing aside with your finger, but suddenly you hear a rather strong shrieking sound, and, suddenly inflating and bending itself, the treacherous creature sinks its jaws into your skin; once you know him, you will be on your guard[ 59 ]and simply pick it up from the scooped-up plants with your tweezers.
If this larva senses danger in the water, it suddenly surrounds itself with a black liquid, so that it escapes the pursuit of its enemies in the ditch, just as the squid does in the sea.
You can easily feed him in your aquarium, he will eat anything and everything; in a short time he is fully grown, and in the same way as with the fringed, you must prepare it to persuade the biting, predatory monstrosity to transform itself into the beautiful, interesting, purring water beetle.
This metamorphosis does not proceed in quite the same way, but the differences you notice, if you breed both beetles, without direction from others, you will light up yourself. Note especially the strange position of the doll in the hollow; the five hooks on the head are supports.
Strange, isn’t it, that with that change not only does the old form disappear, but also the whole nature, the whole way of life of the animal changes.
If you have been successful with your breeding, have the larvae hatched well in the bottles or bowls in which the parents were, then it is important to give all the inhabitants of those bottles another place, or in the end there will be no other choice than either the larvae of Dyticus or those of Hydrophilus. Dyticus is the Latin name for the edged water beetles, the word meaning “diver.”
Better still, it is better to throw all the young larvae back into the same ditch from which the beetles were shoveled.
If you have no desire or opportunity to do so, bring in a few water bugs and some scorpions (see the drawing, pages 19 and 43) or else a piece or two or three sticklebacks; you know, the small one, 4 to 5 cm. long[ 60 ]fish, with 3 or 11 spines on the back. They can be found in masses in every ditch. The boys here call the elf-spiked mud men. Those sweet animals with their pike beaks make sure that the larvae don’t multiply too much; they do that in the ditch too.
When the eggs of Dyticus hatch, in all the ditches and pools of young larvae, the eggs are swarming—a fortnight later, you no longer take them with every shovel. Do the adult-rimmed beetles keep the thorns from growing tall in the water,—these same sticklebacks keep their home among the beetle larvae. Nevertheless, in most ditches these fishes eventually dominate. They are also so pugnacious, and so voracious at the same time, that they depopulate entire ditches until they themselves perish for want of food, for they cannot leave the water in case of famine, like most other ditch animals.
The graceful, quick, usually frantic movements of the spine make it for a while give a cheerful, lively appearance to the aquarium.
His manner of attack and defense, his sociable disposition—they like to swim, if the aquarium is not too small, in schools—everything about the animal attracts and captivates the attention; but your aquarium would soon be empty.
You should in any case keep one pair, if only to observe the way of life, and thereby to explain to yourself how that little creature gains the upper hand so easily in the ditches, also in large puddles and fishponds, yes sometimes in the rivers; so much so that the fishermen or carp breeders are often obliged to hunt them deliberately. For they make the breeding of all other fish impossible, because they devour the fish eggs and the young fish.
The spines on the back stand out here; the three-spined[ 61 ]the most frequent species sets up the dorsal fin, the sharp needles of which are the rays, usually only on attack—the ten or eleven-pricked ones are much wilder and more combative; he has his weapon in readiness almost constantly.
Besides those formidable spines, he has a few more that are not immediately apparent; these lie where the pelvic fins of most other fish are, and are pressed flat against the body towards the rear. Only in mortal danger does he set them up, and the other fish seem not to underestimate the formidable awls that get stuck in their mouths when they fishy want to swallow their smaller tribesmen. The pike even keeps its mouth off the small spine, and the duck rarely touches it. Those side-pins are almost always tucked up on a dead thorn, and you can also feel that it has a well-armed mouth; still better can you perceive the presence of the fine teeth, by hearing,
So armed, so feared, and at the same time supplied with such a good appetite, the fish in the ponds must become troublesome and dangerous to the survival of the rest of the water-dwellers. But in nature the balance is not so easily broken; care has been taken that the trees do not grow into the clouds.
Very often you see thorns that are not nearly as lively as their comrades; they are otherwise very fat and seem healthy too, but it is only in appearance; in a few days the fish will repeatedly lie sideways on the surface, and at last it will die; then small, flat white threads emerge from his body and coil over the surface;[ 62 ]they are a kind of tapeworms that have killed the fish.
But no sooner have the ducks in the ditch or the ponds notice these things, than they shoot at them, and the worms are in and dead; dead, yes, but not quite yet; the worms carried countless eggs, which leave the duck’s body alive, not as eggs, but as tiny creatures, visible only with a magnifying glass; they twist and writhe through the water with the aid of fine cilia, and when they breathe through the spines they pass again between their gills and so into the body, where they develop again into worms.
Thus many thorns perish in the pond, but their death is not wholly useless to the other thorns, though it is bad for those who suffer that fate; in this way an excessive increase is prevented, which in the end was to result in the starvation of all.
Now especially, when you select a pair from a large number of spines, to keep in the aquarium, take care that you take healthy ones; if you find that one of them swims very much to silk, take it out of the bottle before it dies; it seems to be true that the eggs of the spiny worms must first pass through a duck’s stomach in order to be dangerous to other thorns; but that is not yet certain, and there are other fish parasites which may affect your diseased spine; they could also infect the others.
A parasite that is often found on sticklebacks in Amsterdam, I have drawn here very enlarged. The boys call the animal spiny bone; really a good name. The parasite is as flat and round as a bone, but the size[ 63 ]is no more than half a centimeter. Nor is the thorn bone, of course, a fish; it is a crustacean, related to the daphnias, cyclops, shrimps, water jumpers and so many other freshwater crustaceans.
Spiny bone.
Spiny bone.
Fish parasite, which sucks on the stickleback. (Greatly enlarged; the animal is 3 to 4 mm at the most).
I told you to take a pair, a male[ 64 ]and a female, or, as it is called among fishes, a homer and coulter; you can easily distinguish the male by the color in May, June or July; his throat and chest then adorn with golden-red, purple, and purple colors; he is also much more rambunctious than the females; he attacks everything, and incessantly chases the females apart, who often hide together in a corner of the water-bowl and hardly dare to appear.
Take such a awake little fellow aside, give him one, at the most two large females for company. Now especially take care of small aquatic plants, duckweed, hornwort or yarrow, or even better a small amount of water threads; such are the very curious names of those fresh green thread-like plants which you can find in every ditch and which get caught in the net with every spade. The farmers also call them flag or flap; it is they who in the autumn form those yellow sheets on the water.
Now do not disturb your creatures, always look at their actions from a distance; if you have but a little patience and luck at the same time, one fine June day, in the middle or in a corner of the aquarium, you notice a tangle of interwoven water threads, the size of a walnut. On closer inspection you notice that it is a lying barrel without a bottom or lid, with the male keeping watch.
If he stays close to the nest all the time—you understand that the green tube is something like that—then you have a good chance of seeing an attractive natural scene played out; I remember seeing it once as a little schoolboy in an aquarium that stood in front of a watchmaker’s shop cupboard in my hometown; at a school, which I came to later, we also had thorny nests for years in a row. The nest that the ten-spined species makes is rarely on the ground.[ 65 ]
The male incessantly chases after the female, corners her, bites her out again, until he succeeds in driving the female right through the open nest; but the opening is a bit narrow, the female can barely get through it, she stays with her spines in the wires and… lays her eggs in the nest.
But now it has to come out again, it gets a few bites in the tail, it is gone; don’t stay near either, nay, a long way off: egg thief as it is, it wouldn’t spare its own eggs, but the watchful male is on his guard—he knows his people.
A few times he slides through the barrel himself; while doing so he lets some roe liquid (you know the roe from the herring) fall from his body onto the calf; the eggs are thereby fertilized, as they say; without that roe liquid no young fish would hatch; any more than young plants can come from seeds again, unless pollen has touched the pistil of the flower; in the pistil these seeds, like white eggs, were present.
When the male has worked his way out of the nest, he narrows the two openings a bit and continues to cross in the periphery; anyone who comes near is driven off with spiky thorns.
After a week, sometimes earlier, depending on the temperature of the water, the young fish hatch; although they look a bit strange at first because of the thick head and a kind of bag hanging from the throat, they are fish after all; we are not dealing here with a metamorphosis, that is clear.
When the fish are about a centimeter in size, the caring father widens the openings of the nest, and the young are allowed to go outside for a while; it seems[ 66 ]a cloud of mist in the light green water. Just a few more days—and Daddy’s going for a swim with his family. Woe to the female or the beetle or the salamander that comes too close to the school of little ones; the male snaps frantically, his spines being brought into a threatening position every moment.
Even if there are water plants in the ditch or in the aquarium, the three-spined thorn still builds its nest on the bottom. When the eggs are in it, he washes seed grains over it, so that not much of it can be seen. Only a small opening in the bottom, from which some root fibers or blades of grass protrude, indicates the place where the nest is hidden. Yet you can find it and become mighty, now that you know its nature and way of life. If you see such a lone thorn in its wedding suit swimming frantically in the same place in May or June, you can be sure that its nest is not far away.
Slowly put your stick in the water—the thorn swims madly around it; approach the bottom with the tip and stroke it back and forth—the moment the tip touches the nest, the little creature, now almost entirely purple-red, flies to the bottom, bites the stick and tries to clear it with its beak to bump. So the thorn is not as clever as a lapwing or lark; without much difficulty you can scoop up the nest with its guard, who does not leave it, take it home in your bottle and carefully transfer it to a large aquarium. If the animal, which does not always happen, finds its nest there, it recovers and takes care of it as before. His red color, which he had lost before, is also returning.
Perhaps then you will also have the opportunity to notice how nicely he supplies such a dug-in nest with the necessary oxygen. Sometimes he stands vertically above for minutes [ 67 ]the opening, head down, with all fins and tail bent sideways, drives a steady stream of fresh water into and through the nest.
Nest-building fish are few; in our country only one; and it is remarkable that the quill which lays one, such a small number of eggs, twenty or thirty at the most, and they sometimes come from more than one female. It is clear that the safety of all the hundreds of thousands of eggs that a herring or a cod shoots does not need to be taken care of; if only a small part of it comes out, the fish will not die out.
But the thorn has so few in comparison, that’s why the male takes such good care of it. Therefore? Oh, that’s only in a manner of speaking—the thorn with its golden-red breast, after all, knows nothing about the arrangement in nature. It is not a man who can compare, ponder and judge what is useful to him or his descendants. He does it because he must do it, he cannot do otherwise, the instinct of nature compels him to do it, and—when we see him do it, we admire not only that irrational little fish, but in that little fish the wise arrangement of the living world itself. The one who created that passion in that little fish, or who made sure that it could arise in the course of time.
But how to keep our little ones alive, to watch them wash? That is very difficult in a small bottle, a little less in a large aquarium, but still possible in both.
In all efforts you make to keep your animals or plants alive, always keep in mind that four things are indispensable for this: food, air, light and cleanliness. The latter may sound a bit strange for animals from a mud ditch, but experience will teach you. Everything that is dead, plant or animal, must be removed as soon as possible, or your fish farming will fail miserably.[ 68 ]
The 3 most common types of snail shells in the ditch. pool snail. Swamp Horn Snail and Funnel Snail.
The 3 most common types of snail shells in the ditch. pool snail. Swamp Horn Snail and Funnel Snail.
Now you don’t have to do everything yourself, you can set up a cleaning service without any problem for your pocket money. Put a good amount of small snails in the bottles; they take over most of your job. It doesn’t matter whether they’re ordinary water snails, with more or less elongated shells , — or whether they’re snails with flat shells, the coils of which lie side by side instead of one above the other—post horns, we boys said; they are called planorbis in zoology. See the drawings here. Large snails pay themselves for their services by attacking your aquatic plants, and that is difficult. Although again not so much; because you don’t place expensive or rare plants in a study aquarium.
Also, that damage is again somewhat compensated by the opportunity they give you to check out their peculiar eating manners and movements; their proverbial slowness makes this particularly easy, and such a snail’s pace is even more attached than you might think, viewed so superficially.
In any case, you can safely leave the cleaning of your fish farm to your snails; only large dead animals and plants you must necessarily remove yourself. Even if that happens in the ditch, where the thorns thrive, not by human hands, you must not forget that your best decorated aquarium is still only imitated nature.[ 69 ]
[ 71 ]
As for the light, that’s the easiest thing to do. For a window, if it is possible for one that can be opened, the best place is; but prolonged direct sunlight is harmful, unless you have a large supply of shade-giving plants; floating ones, especially frog-bite or sequoia, are very suitable for shading, and that stuff thrives again wonderfully if you breed many fish; as it in turn uses the carbon dioxide that your animals exhale in the water. So about the same cause that causes the plants to wash so vigorously in a well-populated and sunny schoolroom.
By bringing those floating aquatic plants into the aquarium you have immediately provided your cultivators with the necessary air of life; nevertheless, some submerged plants, such as water wires and waterweed, have to be added. Above all, water wires, which secrete a lot of gas; they sit when the sun shines through them even briefly, even in winter by the stove, full of bubbles of oxygen. This oxygen enriches the air already present in the water; it is continually pressed into the mouth, and the gills pushed out again; notice how the pectoral fins are incessantly moving (even when your fish are standing still) to drive away the spent water, and to bring in others.
Sometimes uninvited plants come into your bottles, just when they are well lit. At first light green spheres sink, like very small pinheads through the water; those dots of green remain on the bottom, or settle against the sides. Gradually a light green fitting now covers the glass walls; that does the fish more good than harm; they are tiny plants of the same kind as the water threads, they are called algae; but they prevent you from watching the animals, which is why it is doable in the first place.[ 72 ]
Goldfish and bitterlings like to eat algae, but that would immediately kill the young farmed fish, so that’s not possible.
Well, put some more and some bigger snails in the water, they mow that algae meadow very nicely; their tongue goes incessantly along the glass, leaving bare streaks. On the other hand, they put on something else, jelly-like, elongated, translucent masses a few centimeters long; if you have a good magnifying glass you can, after a few days, clearly discover small snails with shell and all, and monitor their development from the eggs from day to day.
Those snail eggs are immediately a sought after food for your young sticklebacks, as well as mosquito larvae, which can be scooped everywhere in masses.
That I also mentioned food as conditions for keeping the newly hatched fish alive may seem a bit silly to you. Yet not long ago someone once asked me how it was that his fish in the aquarium died one after the other. I mentioned all sorts of things that he might have omitted, but… it certainly wasn’t, and it wasn’t that either.
“Perhaps you are giving them too much food?” I asked.
“Food?” he said. “No, that’s certainly not the reason, they get nothing but dune water!”
It’s a shame that such a person does not understand that even fish can die of hunger.
It depends precisely on the food whether the cultivation will be successful; much that the adult fish can eat is unsuitable for the little ones—not the other way around. They can get snail eggs off the glass quite well after about ten days, but before that time food is also needed.[ 73 ]
Now there are usually in the water, usually invisible to the naked eye, the infusion animals—already discovered by Leeuwenhoek—but that supply does not seem to be sufficient and too soon exhausted by the healthy appetite of the young fish.
Better go to a nearby ditch at night on a sunny summer day. You need not walk far, or you will see, close to the side, a reddish cloud in the water; if the ditch is covered by duckweed, gently push it aside, and the cloud will become visible here or there.
A little way from that cloud, put your big bottle upside down under the water so that little or no air escapes, then turn it over in the middle of that cloud. That is not a dangerous job at all, as the cloud is close to the shore, and you can always find a permanent place to stand; otherwise you give your left hand to your comrade who sits on the rampart.
If by any chance you have not been able to get any knowledge with it, or if the side is too steep, then pass your fine-mesh landing net a few times through that floating cloud and turn it over in the water of the wide-mouthed bottle.
You immediately see in your bottle what that cloud consisted of; thousands of roundish creatures hop and shoot at each other; wriggling, antler-like blades serve as jumping feet in one species,—a forked tail in the other; for usually you have created two kinds of daphnia at once: daphnia, those are the round ones with deer antlers—cyclops are called the little ones with a tail and often with two pockets with black dots on either side of the body; these are females with eggs.
If you have maneuvered quickly and deftly with your great jar, it abounds—except for daphnias and cyclops—of all sorts of larger beasts; shrimp-like [ 74 ]translucent jumpers; dragonfly larvae, recognizable by their long tails of air tubes; fat-headed creatures without legs, black with gray belly: they are called bullheads or bullheads here and there in our country; all future frogs, salamanders or toads; turrets of all sorts, having briefly ceased their merry quadrille on the surface; mosquito larvae or pupae, like bucks with horns, tumbling over their heads like mad; and… young quills, which, like those other animals, came to supper in that daphnia cloud.
Above: Daphnias. Below: Cyclops. The copy on the right with two egg bags (loupe magnification to nature.)
Above: Daphnias. Below: Cyclops. The copy on the right with two egg bags (loupe magnification to nature.)
Here we have the natural food for our fish; every day a splash from the stock, and in a short time you will be able to show your comrades with righteous pride adult fish which you have bred from the egg, ab ovo , say the scientists.
And they are not only the staple food for those young spines; the old fishes love them too, and they grow fat and fat; many other fish species also live mainly on daphnias; they are planted with barrels full in carp ponds[ 75 ]about; especially in the lakes the fish would die out very soon if there were no daphnias: research has shown in recent times. Yes, nowadays they can be bought fresh or dried per kilogram abroad, for the convenience of aquarists or fish breeders. That excellent fish food is now also intentionally grown on a large scale there.
In a wasted hour you should look at such a living daphnia in a drop of water with the magnifying glass; that the animal has but one eye, and that is, one that it can turn like a mill, you see very soon; perhaps also, that the greater part of the animal’s body is enclosed in a double shell, resembling a mussel shell, from which the branched blades protrude.
For the rest it is a wriggling and twisting and swinging as if there were a hundred wheels on the animal, all in motion at the same time. Only when the daphnia chooses to rest a moment do you see that in the gap between the shells there are a great number of crustacean legs, which serve for everything but walking. The daphnias and cyclopes are therefore counted among the crustaceans, as are the shrimp-like jumpers which you have created at the same time as the cloud, these are called gammarids; they still give life in an aquarium; but if there are fish in it, their fun does not last long.
If you are still at school, bring the teacher a few daphnias like that, and ask him to show them to you through a microscope. Then it turns out that such an animal is not ugly at all; the mother-of-pearl dishes adorn with all kinds of colors and drawings; moreover, there is something to observe that you do not see every day: the blood circulation in a living, unharmed animal. Closed [ 76 ]at the back, you discover the heart, a red sac which, by alternately contracting and expanding, draws in and expels the bloodstream with vitreous light-red bodies in it; the eggs also look very different than with the loupe.
Gammarus or Waterspringer (Gammarus pulex).
Gammarus or Waterspringer (Gammarus pulex).
It may seem remarkable to you that almost all adult daphnias in your bottle are females with eggs: you will not see the much smaller males until late in the autumn, sometimes at the beginning of the winter. In the summer the eggs of the females hatch animals more like mites or spiders than daphnias; new daphnias emerge from the winter eggs in the spring; these eggs are the only remnant of our tireless hoppers to survive the winter.
It is not only the fishes, bullheads, backswimmers, and the innumerable beetle and dragonfly larvae that thin out the dense throngs of the one-eyed daphnia.
Hidden under the green leaf of the floating duckweed, a monster lurks those unfortunate creatures, unparalleled in our freshwater ditches or puddles. Only in the high seas does it find its equals, but in gigantic proportions.
You may have heard of the giant polyps that entwine the pearl diver with their long feeler arms, so that his comrades in the boat expect his return to the surface in vain; whether you have[ 77 ]ever seen a picture of the kraken, those fabulous monsters from the North Atlantic, who grip the ship around the masts with their giant arms and pull it with irresistible force into the depths; or else you must have read of the squids, those flesh-sacks with eight or ten arms, which float through the water like slack ropes, until a fish, a lobster, or a tortoise comes within the reach of the feeler’s arms; these tentacles then suddenly begin to writhe like snakes and suck themselves on the prey with hundreds of suckers; in their coils the captive animal suffocates, it is carried to the mouth of the flesh-bag, where it soon disappears.
A Water flea or Daphnia (highly magnified).
A Water flea or Daphnia (highly magnified).
o. eye m. mouth h. heart d. gut egg. egg sac
Such a monster, but fortunately for most ditch dwellers, in very small size, also inhabits our regions. It is the freshwater polyp, an animal of at most an inch in length, as far as the body is concerned.
Leeuwenhoek was already the first discoverer of the existence of this strange creature. Its discovery was forgotten, and a good hundred years ago, I believe, it was rediscovered by one who did not know the works of our compatriot. It is no wonder that the creature remained unknown for so long; who are not exist [ 78 ]suspect, it will not find light; even if one knows that polyps live in some ditch, it is difficult to find them.
Leeuwenhoek had already noticed several times that objects which he thought to be plants cling to the glass of his flask of ditch water. They were green or brown stalks, an inch in length, and as thin as a knitting needle, often thinner, though somewhat thicker at the top than at the bottom; from the thicker part sprang six or eight very thin, tortuous, cobweb-like threads, which spread far out in the water, until they became invisible.
There was movement in those wires, but he attributed this to a weak movement of the water, which was caused by the small infusion animals, which he also discovered.
They lent themselves less well to an examination with his microscopes; for if he carefully took such a twig out of the water, the whole thing collapsed into a jelly-like brown ball, the size of a pinhead, and there was little remarkable about it under the microscope.
He kept a careful eye on the enigmatic little plant for a long time, and soon noticed that there was a lump here and there on the stem; that nodule grew and became a twig quite like that on which it had grown. It remained with the old one for several hours, sometimes even for a day. twig joined, then let go and, a little way from the first, attached itself to the glass in the same way with its foot.
This mode of reproduction reminded Leeuwenhoek of the mode of reproduction of some crops, and it strengthened his belief that he was also dealing here with a plant. Yet he was not at peace with it;[ 79 ]time and time again he returned to his queer little plant, and then perceived that it must have moved in some way.
One day, dressed as usual in his chintz dressing -gown , sitting before his large table at the window, and having given orders not to disturb him in any way, he noticed that the little plant was moving; Leeuwenhoek had already seen a lot of new and wonderful things happening before his eyes, but the sight shocked him greatly, the glass trembled in his hands.