. Economic entomology for the . Ceraphron triticutn, parasitic in wheat plant-louse. They undoubtedly check injurious species, but also each other ; in this way preserving a balance from year to year which keeps all the forms at about the same relative level. Of course the " hyperparasites," as the forms infesting the other parasitic species are termed, are distinctly injurious from the agriculturist's stand-point; perhaps even more so than the forms actually feeding on vegetation. The question of making economic use of parasites belonging to this order has been frequently d
. Economic entomology for the . Ceraphron triticutn, parasitic in wheat plant-louse. They undoubtedly check injurious species, but also each other ; in this way preserving a balance from year to year which keeps all the forms at about the same relative level. Of course the " hyperparasites," as the forms infesting the other parasitic species are termed, are distinctly injurious from the agriculturist's stand-point; perhaps even more so than the forms actually feeding on vegetation. The question of making economic use of parasites belonging to this order has been frequently discussed, but no practical results have yet been obtained. Occasionally several species attack a single host, and yet, withal, they seem to produce no effect upon it in the long run. Even though we may breed out of a lot of caterpillars more parasites than butterflies or moths, in the season following the caterpillars will be just as abundant as they were the year before. Just where the checks to parasite
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