Economic entomology for the farmer Economic entomology for the farmer and the fruit grower, and for use as a text-book in agricultural schools and colleges; economicentomol00smit Year: 1906 PROPEBTY ur THE INSECT ifD^LD. 383 that infest aphids. If, at any time during the summer, a leaf badly infested with plant-lice be examined, there will be usually found a few specimens that seem abnormally swollen and livid gray in color rather than green or yellow. Such specimens are parasitized, and if they be removed to a closed vessel, there will be found in it, in a few days, minute blackish or brown
Economic entomology for the farmer Economic entomology for the farmer and the fruit grower, and for use as a text-book in agricultural schools and colleges; economicentomol00smit Year: 1906 PROPEBTY ur THE INSECT ifD^LD. 383 that infest aphids. If, at any time during the summer, a leaf badly infested with plant-lice be examined, there will be usually found a few specimens that seem abnormally swollen and livid gray in color rather than green or yellow. Such specimens are parasitized, and if they be removed to a closed vessel, there will be found in it, in a few days, minute blackish or brown wasp-like creatures, and on each of the infested plant-lice will be seen a little round hole, which shows where the insect emerged. They are usually examples of minute Braconids, and are the most im- portant of those natural checks that prevent the increase of plant- lice above a certain point. Unfortunately, that point does not coincide with the limit at which the insects become injurious to the farmer ; hence, though the parasites accomplish their pur- pose, they do not, therefore, confer any direct benefit upon him. At almost all periods during the season, but especially late in summer or fall, caterpillars may be seen, bearing upon their backs and sides white or yellowish, egg-shaped bodies. These are often supposed to be the eggs of the caterpillars, but as a matter of fact they are cocoons of Microgaster or Apayiteles, little parasites belonging to this family ; and if the caterpillar be confined for a few days it will be noticed that from the tips of each of these egg-shaped bodies a little circular lid is lifted off and a Httle wasp emerges. If, late in summer, a number of the large sphinx caterpillars infesting potato or grape-vines are watched when they yet show no signs of infestation, one may fre- quently see the little larvae boring their way through the skin, wriggling until '^'• they have emerged for more than half their length, and it is then easy to watch the
Size: 2198px × 910px
Photo credit: © Bookworm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
