THE PHYLLOXERA.

Poverty Bay Standard, Volume IX, Issue 916, 9 February 1881, Page 3

THE PHYLLOXERA.

The following is an account of the habits of this insect, which has been the cause of so much mischief on the Continent of Europe.

The insects are found both on the leaves and roots, and there is a considerable difference in their appearance in the two situations. The forms that appear on the leaves have been for convenience termed gallicola, those on the roots radicicola. The gall or excresence produced by the insect is simply a fleshy swelling on the under side of the leaf, more or less wrinkled and hairy, with a corresponding depression on the upper side, the margin of the cup being fuzzy, and drawn together so as to form a fimbriated mouth. It is sometimes cup-shaped, but sometimes greatly elongated or purse-shaped, and about the size of an ordinary pea. They are formed by the mother insect in spring, and her eggs are deposited in them, The young are speedily hatched, and scatter themselves over the vine, forming similar galls, and laying eggs as their parents did before. This process is continued for five or six generations during the summer, and in autumn the remaining insects descend to the roots, where they attach themselves singly or in groups, and thus hybernate. The radicicola, or root-inhabiting - type, presents itself in two principal forms. The newly hatched larvae are undistinguishable in all essential characters from those hatched in the galls, but in due time they shed the smooth larval skin, and acquire raised warts or tubercles, which at once distinguish them from gallicola. In the development from this point the two forms are easily separable. The first or mother form never acquires wings, and is occupied during its lifetime in laying eggs. The second or more oval form is destined to become winged ; after feeding a short time they make their way to the light, crawl over the ground and over the vines, and finally shed their last skin and assume the winged state. These are most abundant towards the autumn, and until the vines cease growing. The majority of them are females: they |lay eggs that are both male and female. The insects hybernate during the winter in the state of larvae and a few eggs, and in spring commence to feed on the roots and deposit eggs as before. The result which follows the puncture of the root insect is an abnormal swelling, the roots gradually dying and going to decay. During the first year of attack there are scarcely any outward manifestations of disease, though the fibrous roots, if examined, will be found covered with nodosities. The second year all these fibrous roots vanish, and the insects not only prevent the formation of new' ones, but eventually cause the larger roots to become disorganised and rot. At this stage the outward symptoms of the disease become manifest in a sickly yellowish appearance of the leaf, commencing at the margin, and a reduced growth of cane. In another year or two the vine is killed, and the insects have travelled through the soil and on the surface to the neighboring vines, or been wafted on the wind to distant vineyards.