Word: pupa
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
Scientists anxious to find a safe but powerful pesticide have long been fascinated by the juvenile hormone that is secreted by insects. At certain stages of an insect's life cycle, the hormone must be present to regulate growth and control the transformation from larva to pupa. At other times the hormone must be absent, or the insect will develop abnormally and never reach sexual maturity. If a sufficient dose is given to a mature female, it can make her sterile for life thus eliminating future generations. The trouble is that the hormone, synthesized in commercial quantities and sprayed...
WHILE dissecting pupae in search of the liquid's production site, he noticed a pair of long, very thin tubes in the front part of the pupa. These were the remains of the silk-producing tubes of the caterpillar. They led to a single opening on the moth's face just underneath the mouth. It was impossible to tell exactly where the liquid comes from since the first drop appears suddenly and covers the face. Yet the mouth and the old silk tubes were the only two openings and the mouth could be discounted because Kafatos had already shown that...
...glands. The old silk tubes produced the inert part of the liquid while a special gland on the face secreted the enzyme itself. Kafatos substantiated these findings by proving that the moths could produce the enzyme even if the silk tubes were removed at an early stage of the pupa's development...
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...
...code. The great store of hereditary information that DNA contains, says Karlson, is not needed all at once. It comes into play gradually, as if it were being looked up, item by item, in a book of instructions. When the time comes for a larva to turn into a pupa, ecdysone secreted by its glands circulates among the cells and comes in contact with the long, ropelike molecules of the DNA in the chromosomes. The hormone affects only those parts of the DNA molecule that contain a few items of chemical instructions needed for metamorphosis. The parts become suddenly active...