. A manual for the study of insects. Insects. l6o THE STUDY OF INSECTS. (My^sus per^si-cae). The last three are almost invariably attended by ants. The Plant-lice of the genus Lachnus (Lach'nus) are usually found on the limbs of trees and shrubs. To this genus belong our largest Aphids, some of them measuring one-fourth inch in length. Figure 199 represents one of these enlarged. ^ r ' Some species of plant-lice live both on riG. igg.—Lachnus, ^ ^ the roots and on the leaves of plants. One of these is the Grape Phylloxera, Phylloxera vastatrix (Phyl- lox-e^ra vas-ta'trix), which is the most im
. A manual for the study of insects. Insects. l6o THE STUDY OF INSECTS. (My^sus per^si-cae). The last three are almost invariably attended by ants. The Plant-lice of the genus Lachnus (Lach'nus) are usually found on the limbs of trees and shrubs. To this genus belong our largest Aphids, some of them measuring one-fourth inch in length. Figure 199 represents one of these enlarged. ^ r ' Some species of plant-lice live both on riG. igg.—Lachnus, ^ ^ the roots and on the leaves of plants. One of these is the Grape Phylloxera, Phylloxera vastatrix (Phyl- lox-e^ra vas-ta'trix), which is the most important enemy of the grape. The presence of this insect is manifested by the vines in two ways: first, in the case of certain species of grapes, there appear upon the lower surface of the leaves fleshy swellings, which are more or less wrinkled and hairy; these are hollow galls, opening upon the upper surface of the leaf, and containing a wingless agamic plant-louse and her eggs; second, when the fibrous roots of a sickly vine are examined, we find, if the disease is due to this insect, that the minute fibres have become swollen and knotty; or, if the disease is far advanced, they may be entirely decayed. Upon these root-swellings we also find an agamic, wingless, egg-laying plant-louse, the author of the mischief. The insects found upon the roots differ slightly from those found within the galls, but their specific identity is now generally accepted. Owing to the great injury which this species has done to the vineyards of France, hundreds of memoirs have been published regarding it. But as yet no satisfactory means of destroying it has been discovered. The difficulty lies in the fact that the insecticide must be one that can penetrate the ground to the depth of three or four feet, reaching all the fibrous roots infested by the insect. It must be a substance that can be cheaply applied on a large scale, and it must alsoi be something that will kill the insect without injury
Size: 2465px × 1014px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectinsects, bookyear1895
