Insects. 



GRAPE MANUAL. 



Phylloxera. 53 



Fig. 75. MOTHER GALL-LOUSE : 

 ventral and dorsal views. 



By the end of Sep- 

 tember the galls are 

 mostly deserted and 

 those which are left ap- 

 pear as if infected with 

 mildew, and eventu- 

 ally turn brown and 

 decay. The young lice 

 attach themselves to Fig. 74 



the roots, and thus hi- NEWLY HATCHKD GALL-LOUSE: 

 bernate. It is an im- a > ventral ; -6, dorsal view, 

 portant fact that the gall-inhabiting insect occurs only 

 as an agamic and apterous female form. It is but a 

 transient summer state, 

 not at all essential to 

 the perpetuation of the 

 species, and does, com- 

 pared with the other or 

 root - inhabiting type, 

 but trifling damage. It 

 flourishes mostly on the 

 Riparia, more especial- 

 ly on the Clinton and 

 Taylor; its galls have also been noticed on many 

 other varieties. In some seasons it is even difficult to 

 find a few galls on the very vines on which they were 

 very abundant the year before. 



The root-inhabiting type of the Grape Phylloxera 

 hibernates mostly as a young larva, attached to the 

 roots, and so deepened in color generally as to be of a 

 dull brassy brown, and therefore perceived with diffi- 

 culty, as the roots are often of the same color. With 

 the renewal of vine-growth in the spring, this larva 

 moults, rapidly increases in size, and soon commences 

 laying eggs. These eggs, in due time, give birth to 

 young, which soon become virginal, egg-laying moth- 

 ers like the first, and, like them, always remain wing- 

 less. Five or six generations of these egg-bearing 

 mothers follow each other, when, about the middle of 

 July, in the latitude of St. Louis, some of the individu- 

 als begin to acquire wings, and continue to issue from 

 the ground until vine-growth ceases in the fall. Hav- 

 ing issued from the ground while in the pupa state, 

 they rise in the air and spread 

 to new vineyards, where they 

 lay from three to five eggs, and 

 then perish. In the course of a 

 fortnight these eggs, which are 

 deposited in the crevices on the 

 surface of the ground, near the 

 base of the vine, and upon the 

 * X *H^* OVl l ea ves, especially on the under 

 \~Jz ^'&\<$K~\ side, produce the sexual indivi- 

 * duals, which are born for no 

 other purpose than the repro- 

 duction of their kind, and are 

 without means of flight or of 

 taking food. They are, however, quite active and 

 couple readily. 



The female lays a single egg, which has been called 

 the ''winter egg," from the fact that it generally 

 passes the winter unhatched. It may, however, hatch 

 the same season that it is laid. It is generally hidden 

 in the crevices and under the loose bark of the older 

 wood, but may also be laid in other situations, and 

 even on old leaves on the ground. There hatches from 



Fig. 76. 



MALE PHYLLOXERA ; 

 ventral view. 



it the "stem-mother," which either goes directly on 

 to the roots to found a root-feeding colony, or, under 

 favorable circumstances, founds a gall-inhabiting 

 colony on the leaf. 



Every piece of root having rootlets taken from an 

 infected vine during August or September will pre- 

 sent a goodly proportion of pupse, and a glass jar filled 

 with such roots and tightly closed will daily furnish, 

 for some time, a dozen or more winged females, which 

 gather on the side of the jar toward the light. We 

 may gather some idea from this fact, of the immense 

 number that disperse through the air to new fields 

 from a single acre of infected vines, in the course of the 



Fig. 77. 



TYPB RADICOI.A: showing the tubercles by 

 which it is distinguished from Sallicola. 



late summer and fall months. We have, therefore, the 

 spectacle of an underground insect possessing the 

 power of continued existence even when confined to 

 its subterranean retreats. It spreads in the wingless 

 state from vine to vine and from vineyard to vineyard, 

 when these are adjacent, either through passages in the 

 ground itself, or over the surface ; at the same time it 

 is able, in the winged condition, to migrate to much 

 more distant points. 



If to the above account we add that occasionally in- 

 dividuals, under certain conditions, abandon their nor- 

 mal underground habit, and form galls upon the leaves 

 of certain varieties of grape-vines, we have in a general 

 way the natural history of the species. 



The annexed figure (78) shows the abnormal swelling 

 of the rootlets which follows the puncture of the root- 

 louse ; they eventually rot, and the lice forsake them 

 and betake themselves to fresh ones. As these decom- 

 pose, the lice congregate on the larger parts beyond, 

 until at last the root-system literally wastes away. 



During the first year of attack there are scarcely any 

 outward manifestations of disease; only the second 

 and third year when the fibrous roots have vanished, 

 and the lice not only prevent the formation of new 

 ones, but settle on the larger roots, which also eventu- 

 ally become disorganized and rot do the outward 

 symptoms of the disease become manifest in a sickly, 

 yellowish appearance of the leaf, and a reduced growth 

 of cane ; and the vine dies. When the vine is about 

 dying, it is generally impossible to discover the cause 

 of the death, the lice having previously left for fresh 

 pasturage. 



As is frequently the case with inj urious insects, the 

 Phylloxera shows a preference for and thrives best on 

 certain species, and even discriminates between varie- 

 ties, or what amounts to the same thing, practically, 

 some species, or varieties, resist its attacks, and enjoy 

 relative immunity f.om its injuries. A knowledge of 

 the relative susceptibility of different varieties to the 

 attacks and injuries of the insect is therefore of para- 

 mount importance. 



