. Elementary studies in insect life. Insects. 218 ELEMENTARY STUDIES IN INSECT LIFE himself. Insects primarily depend upon vegetation for sustenance. So rapid are their powers of assimilation and so prodigious their efficiency for multiplication, that, were they to go on unheeded and unchecked, they would in the struggle for existence overcome FIG. 181. Cecropia larva bearing cocoons of a parasitic insect, an ichneumon fly. ?3'. Such is not the case, however. Insects are as a house divided, one part preying upon and destroying the other; the two succeed each other like wave upon wave
. Elementary studies in insect life. Insects. 218 ELEMENTARY STUDIES IN INSECT LIFE himself. Insects primarily depend upon vegetation for sustenance. So rapid are their powers of assimilation and so prodigious their efficiency for multiplication, that, were they to go on unheeded and unchecked, they would in the struggle for existence overcome FIG. 181. Cecropia larva bearing cocoons of a parasitic insect, an ichneumon fly. ?3'. Such is not the case, however. Insects are as a house divided, one part preying upon and destroying the other; the two succeed each other like wave upon wave. Parasites, finding innumerable insects to prey upon, increase so rapidly as to devour their means of support. They in turn succumb and the host rallies, only to be again defeated. So the struggle goes on forever. Parasites do not confine themselves to forms gaining an independent livelihood, but attack those of like habits as themselves--a phenomenon usually termed hyper-parasitism. jSTot only do parasites attack para- sites, but cases of secondary parasitism are numerous, tertiary parasitism is not rare, and quaternary para- sitism has been suggested as possible. Insect parasitism is of wide prevalence. A few years since the trees of the city of Washington, D. C., were almost wholly de- foliated by the white-marked tussock-moth. The great numbers of bodies of these insects attracted and fur- nished food for parasites, until in the second season ninety-seven per cent, of the caterpillars were destroyed. 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 Hunter, Samuel John, 1866-1946. Topeka, Kan. , Crane & company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectinsects, bookyear1902
