New Britain Herald Newspaper, August 4, 1928, Page 11

i § § The “Cannibal” Nematode, Which Feeds Upon Others of Its Kind. Note the Relatively Enormous Mouth, as the Creature Writhes, Head Downward, Toward Its Prey. (Photo Greatly Enlarged.) By RENE BACHE. NIMALS that assume strange and mon- A strous forms. So innumerable that even the hosts of insects are by comparison only a few. Yet hardly anyone knows anything about them. It is not merely because they are small. species of them are several feet long. It is not because they are harmless. They are wholesale destroyers of the crops and are respon- sible for some pf the worst diseascs that afflict mankind. b For some years past the Department of Agri- culture has been making an exhaustive stydy of them, in the hope of finding means whereby they can be successfully fought. It is now pre- pared to launch a new clmr‘-im against the noxious creatures with the hope of stamping them out. esc “bugs” are called nematodes. There are hundreds of thousands of species, a great major- ity of them quite small. % Sometimes it happens that the housewife finds her vinegar swarming with tiny eel-like They are called “vinegar eels.” But they are not worms, not yet eels. They are nematodes, hatched from eggs which, floating in the air, have found their way into the vinegar. The top three inches of soil in an average ten- acre field contain enough nematodes if placed end to end in single file to form a continuous procession reaching around the world. Any bit of soil or scrap of mud from the bot- tom of a pond or stream, when examined with a magnifying glass, will be seen to contain slender animals which whip themselves about by contor- tions of their bodier. It is hard to find any !place where nematodes do not exist. They are found in the dryest deserts. They live at great depths in Alpine lakes. They have been thawed out of Antarctic ice, near the South Pole. Their bodies are almost as transparent as if made of glass, and some of the larger species, several inches long, assume remarkable forms. . Thus, for example, the “dragon” nematode gets its name from the resemblance it bears, though in miniature, to the fire-breathing mon- stres of fable. Some The “shark” nematode s a ercature of prey and a cannibal— a devourer of its own kind. Its fm-n;lidable jaws are armed with fierce re-curved teeth. The “cobra” nematode has a big fang in the middle of its upper jaw for piercing, supple- mented by batteries of small grinding teeth for chewing plant roots. “The “double-digger” carries on the front of its head a solid piece of armor so fashioned that it can be used for chopping. With this tool it can chop both ways, down and up, hacking itself along through the soil or through the tissues of the plants it attacks. The blood-sucking, intestinal parasite called the “hookworm,” which afflicts whole popula- tions in the Southern States, usually entering bare feet and boring in until it reaches the body cavity, is a nematode. In the Philippines and other tropical countries a threadlike nematode finds its way Into people’s bodies, multiplies in enormous numbers, blocks the lymph channels and thereby causes the frightful swellings of elephantiasis. he “trichina” nematode, which is a danger to human beings, renders necessary the Govern- ment inspection of all pork at a cost of hundreds of thousands of dollars per annum, = Dr. N. A. Cobb, the Government’s principal expert in the study of this class of anir:als, ngyl that nematodes may be suspected, “with good show of reason,” to be carriers of cancer. Losses of sheep and cattle from attack by nematodes run far up into millions of dollars annually, and chickens are swept away by them in flocks. _Thus it will be seen that these creatures con- stitute both an agricultural problem and a publie health problem. The jsws of nematodes—of those, that is to say, which have them—are not arranged in pairs like those of other animals, Usually there are three, working upon each other in triangular {fashion, and not infrequently armed with fero- cious-looking teeth. In stqme sneciefs the mouth is provided with a projecting spear for puncturin; an internal mechanism tlnt" SiEpaectsliy serves the purpose of a pump, for sucking plant juices, or, in some instances, blood. In moist meadows and swamps are found great numbers of seal, lx:]:nlten called “iotas,” wlhicz ive spears exceptionally long and powerful, ) - rusade o _TUShike. oxious 'ema How the Department of Agriculture Hopes to Destroy the Glassy Monsters That Devour Our Crops and Infect Human Beings with Perilous Maladies. Many great cities filter their water supplies through sand. The water, after settling in basins provided for the purpose, is run through three feet of sand, and, as delivered to consum- ers, is supposed to be absolutely pure, Unfortunately, the filter beds of sand may be propagating grounds for multi- tudes of nematodes, and every glass of water drunk by the citizen has passed through myriads of them. To prove the fact is easy. If a rag be tied, bag fashion, to a faucet o night some of the “worms” will be found in it in the morning. They are harmless; nevertheless, the idea is not agreeable. In the top layer of one of the sand filter beds in Washington, Dr. Cobb found the nematodes in such numbers as to represent hundreds of millions per acre. As already said, nematodes do great damage to the crops. Most destructive of them all is the “gallworm,” a very tiny species, only one-twen- tieth of an inch long. By forming galls on the roots of cultivated plants it reduces crop yields enormously. It levies a huge tax on every kind of crop. A so-called “normal” crop is what the farmer gets after the gallworm has taken its toll. It has long been a matter of familiar knowl- edge that the same kind of crop cannot be profit- ably produced year after year on the same picce of land. But the rea- son why has not here- tofore been under- stood, It is because of the activities of nematodes. Suppose the crop to be potatoes. Nematodes of kinds that prey on potato plants multiply rapidly in the potato field, and after a while there are so many of them that the potato plants can no longer pros- per. The potato plants are obliged to move. So the farmer uses another field for growing potatoes, and where the potatoes were he sows beans. The nematode enemies of the potato do not care for beans and die out for lack of the food they require. So the beans thrive until, after a while, their own nematode foes have a chance to multiply and become too many for them, so to speak. Then the beans must move. Whereupon the farmer can grow potatoes again on that same area and get a good crop. Thus the reason behind the practice of ‘“rotation of cr?s" is now for the first time explained. he eggs of all nematodes, w! ig or little species, are microscopic, comp: ize to spores of fungi or the larger bacteria. They float about in the air; they may be seen as mites in the sunbeam; they are present in incalculable numbers ¢ where. The dust in our houses is full of them. They may be dried for indefinite years and yet preserve their vitality, hatching out young when moistened. There is a kind of nematode which makes grasshoppers its special prey. Armed with a spear, it bores its way into the inscct until, finally reaching the body cavity, it coils itself. A Nematode Which Preys on Grasshoppers and Is, Therefore, 8 Friend of Uncle Sam’s, Y Fomwerw Festwe Survies, 1 When full-grown, it is nearly a foot long. A *hopper infested by this parasite is rendercd in- capable of reproducing its kind, and after a while it dies, whereupon the nematode, deserting the corpse, lays a batch of eggs underground, and the young, hatched in the Spring, go after the grasshoppers. Grasshoppers have a tremendous birth- rate, so that every now and then there is a plague of them in one region or another. But, as they gain in numbers, the nematodes multiply at a much faster rate and attack them. The ’hop- pers are killed off, only a relatively few being left, and their par- 7 asitic foes, lacking //?/ ,/ 20,0/ 5 é/l //// // 7 ~ At Left: The “Shark”™ Nematode, Equipped with Savage Jaws and Scaly Skin. prey to feed on, perish and nearly disappear. This gives the 'hoppers a chance to become numerous again and devastating swarms appear. Here, then, is the explanation of the periodicity of grasshopper Vv % plagues. It illustrates the idea that some kinds of nematodes may be useful. Grasshoppers—the locusts of the Bible —do immense damage to crops at times in parts of the West, and it has struck the Department of Agriculture as a good scheme to encourage the activities of that particular species of nematode. Accordingly, at the Falls Church (Va.) Experi- mental Station, nematodes of this species are now being artificially bred. To speak more accu- rately, their eggs are being collected in quantity, the method being to place a single female be- tween two mud pies and wait for her to lay. Inasmuch as one female will produce about half a million eggs in a bateh, it does not require more than a few to yield as many as are wanted for experimental purposes. Although the ’hoppers prefer certain kinds of grasses and grains for diet, they seldom leave anything in the way of vegetation untouched. Trees and shrubs often are stripped by swarms of the "hoppers, and even the wood is not spared. The plan in view is to mix the nematode eggs with grasshopper bait, which is ordinarily bran mash with an admixture of citric acid (the latter very attractive to the insects), and thus te spread among the "hoppers a destructive parasitie infection.