OCR Text |
Show Scientists Attack The "Eighth Plague" make them such unexpected and catastrophic pests." The swarms take flight spontaneously spon-taneously on warm, dry days when their body temperature is high. The muscular activity caused by flight, further raises their temperature. temper-ature. They stop flying when conditions con-ditions change either rain, a drop in temperature, or the coming of night. The swarms travel for great distances. dis-tances. They have been seen as far out at 1,200 miles at sea, and they cover vast areas. Once a plague is well started, it is difficult to stop. Because of Dr. Uvarov's basic discovery about the identity of solitary and gregarious forms of locust, preventative measures have been introduced. These are to find out the special "outbreak areas" and to destroy the swarms there before they take flight. And second, sec-ond, to alter natural conditions so that the swarms never form. The policy put forward by Dr. Uvarov at an international conference con-ference 14 years ago, is still valid: "A rational anti-locust policy should consist in organizing permanent per-manent supervision of every known outbreak area by expert entomologists, who would be able to notice the first signs of a transformation of solitary locusts into the gregarious phase, and to destroy the first small swarms that may appear. If no swarms, however small, are permitted to migrate outside the outbreak areas, no invasion of wide regions such as happen in the past, can occur in the future." A colleague of his comments: "Indeed, the solution of this problem will be found when we will have determined the factors fac-tors which cause the change over from the solitary phase to the gregarious gre-garious phase; and, knowing these factors for each specie, we shall be able to prevent those conditions developing which favor the vast multiplication of these insects." t s by Maurice Goldsmith UNESCO Science Editor The dread locust plague is once again darkening the skies over vast areas of Africa and southwest south-west Asia, threatening millions of impoverished people with famine. This is no novelty for these regions which, from Biblical days, have been devastated periodically by these surging masses of insects. The eighth plague of . ancient Egypt was due to the desert locust. lo-cust. During the last thirty years we have cleared up a great mystery in the life of the locust. No one knew what happened to the locusts lo-custs when they were not swarming. swarm-ing. Dr. B. P. Uvarov of the Anti-Locust Anti-Locust Research Center in London explained what happens. A locust is a kind of grasshopper as an individual not different from other grasshoppers, living a solitary, quiet life. But every now and again he gets together with hundreds upon hundreds of thousands thous-ands of fellow locusts and runs amok. His behavior in a crowd is quite different from his comportment com-portment as an individual. Dr. Uvarov showed that the off-spring of the solitary form when brought up in crowds, in fact the gregarious forms, and vice-versa. This great discovery was the key to the origin of plagues. The first requirement is a period per-iod when conditions are particularly particu-larly favorable for the solitary insects in-sects to live and breed, so that they multiply rapidly. For the desert locust, the crucial condition seems to be extra good rains, so that extra generations can be squeezed in before the country dries up again and breeding stops. But to produce gregarious swarms from the myriads of scattered insects then present, a less favorable period must follow the more favorable one. When that happens, the insects can find suitable suit-able living conditions only in res- tncted areas, and they get very crowded there. They become attracted to each other, yet at the same time hypersensitive hyper-sensitive to each other's movements, move-ments, so that their excitement grows until they cannot keep still. In a few generations they have ceased to be solitary grasshoppers and have gathered into great swarms which sally forth on the restless, far-ranging flights which |