. Biology and man. Biology; Human beings. After Bureau of Entomologj and Plant Quaiantine, A DOUBLE-FACED ENEMY The destructive black stem rust of wheat spreads rapidly through the summer by means of spores, in two or three successive generations. The two-celled spores that survive the winter cannot infect wheat. In the spring these spores produce short hyphae, which bear multitudes of rather tender spores, which are also indifferent to wheat eliminate mosquitoes, which depend upon wetness for their early stages— egg, larva and pupa. And in doing so, as we all probably know, we interf
. Biology and man. Biology; Human beings. After Bureau of Entomologj and Plant Quaiantine, A DOUBLE-FACED ENEMY The destructive black stem rust of wheat spreads rapidly through the summer by means of spores, in two or three successive generations. The two-celled spores that survive the winter cannot infect wheat. In the spring these spores produce short hyphae, which bear multitudes of rather tender spores, which are also indifferent to wheat eliminate mosquitoes, which depend upon wetness for their early stages— egg, larva and pupa. And in doing so, as we all probably know, we interfere with the continuity of the malaria parasite or of the yellow-fever virus (see table, p. 620). Fighting Fire with Fire Biologists have found that a most effective way of fighting an epidemic is with a counter-epidemic. Thus, since a trouble- some species is probably kept in check in its native habitat by its natural enemies, we can restore a disturbed balance by finding the natural enemy of our pest. It has been possible to control the destructive Hessian fly by means of the parasitic insect Polygnotus. The gypsy moth has been a constant source of destruction to various cultivated crops since about 1870; it seems to be coming under control with the introduction of the calosoma beetle from France (see illustration, p. 596). One of the first suggestions that insects could be 594. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gruenberg, Benjamin C. (Benjamin Charles), 1875-1965; Bingham, N. Eldred (Nelson Eldred), 1901-. Boston, New York, [etc. ] Ginn and company
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