Word: insectes
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Leader of the expedition that stum bled on the river of insecticide was Harvard Biologist Carroll M. Williams, 50. Recently Williams has been work ing with hormones that are secreted by insects to permit and regulate growth and maturation from egg to larva to pupa to adult. If insect juvenile hor mone comes in contact with larvae at the wrong stage of development, the in sects will not mature. When insects at later stages are treated with growth hor mone, they are killed by developing at too rapid a rate. Moreover, Williams .and other researchers have discovered that lethal equivalents...
Williams quickly hypothesized tint the Rio Negro might in effect be an immense tea, pontaining infusions of plant and tree substances similar to the insect hormones. Scooping up the dark river water, Williams and his colleagues, Professors Fotis Kafatos of Harvard and David Prescott of the University of Colorado, freeze-dried and boiled the water to concentrate the chemicals in it, extracted them with solvents, then injected the resulting solution into immature cockroaches. Sure enough, the roaches all died without reaching sexual maturity...
Since many insects have become immune to sophisticated chemical insecticides, Williams' discovery may well provide a crucial weapon in man's interminable war with disease-carrying and crop-ruining insects. But there are problems yet to be solved. So effective are the hormones and their plant-made equivalents, that sprays or dusts containing even minute amounts will kill any insect, including those helpful to man and essential to the functions of nature. The reason that all insects are not wiped out in the Rio Negro area is that not all of them come into contact with the insecticide...
This "juvenile hormone" is needed in the early stage of growth, but must be absent later for the insect to metamorphose. If this hormone is artificially forced on the but, it will not reach sexual maturity...
Mistaken for Grasses. Supported by an $80,000 grant from the U.S. Agriculture Department, which was concerned about the possibility that the disease might spread to the U.S., Harpaz finally identified the virus carrier as a tiny plant hopper named Delphacodes striatellus. The insect, he discovered, was not particularly fond of corn, preferring the sap of barley, wheat and oat plants during winter and wild grasses in the summer. But while moving from its winter-to summer-plant hosts, the plant hopper frequently plunged its stylet into young corn seedlings in the mistaken belief that they were wild grasses...