GRAPE MANUAL. 



27 



[Under side of Leaf covered with Galls.] 



dredth part of an inch long, and not quite half as thick. 

 She is about .04 inch long, of a dull orange color, and 

 looks not unlike an immature seed of the common purs- 

 lane. The eggs begin to hatch, when six or eight 

 days old, into active little beings, which differ from 

 their mother in their brighter yel- 

 low color, more perfect legs, etc. 

 Issuing from the mouth of the 

 gall, these young lice scatter over 

 the vine, most of them finding 

 ftieir way to the tender terminal 

 leaves, and commence pumping 

 up and appropriating the sap, 

 forming galls and depositing eggs, 

 as their immediate parent had 

 This process con- 







[TYPE GALLIC9LA : c, 

 egg; d, section of ,i ftnp hpforp 

 gall; e, swelling of done l 

 tendril.] tinues during the summer, until 



the fifth or sixth generation. 

 Every egg brings forth a fertile female which soon be- 

 comes wonderfully prolific. 



By the end of Sep- 

 tember the galls are 

 mostly deserted and 

 those which are left are 

 usually infected with 

 mildew, and eventu- 

 ally turn brown and 

 decay. The young lice 

 attach themselves to HATCHED 



the roots, and thus hi- ventral; b, dorsal view.] -; 

 bernate. It is an important fact that the gall -inhabit- 

 ing insect occurs only as an agamic and apterous female 

 form. It is but a transient summer state, not at all es- 

 sential to the perpetua- 

 tion of the species, and 

 does, compared with the 

 other, or root-inhabit- 

 ing type, but trifling 

 damage. It flourishes 

 only on the Riparia, 

 more especially on the 

 Clinton and Taylor ; a 

 [MOTHER GALL-LOUSE; ventral few of its galls have 

 and dorsal views ] been noticed on some 



other varieties, and abortive attempts are often made 



to found them on others. And in some seasons it is 

 even difficult to find a few galls on tbe 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 as generally to be of a 

 dull brassy brown, and therefore with difficulty per- 

 ceived, 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 rnfothers 

 like the first, and like them, always remain wingless. 

 Five or six generations of these egg-bearing mothers 

 follow each other, when, aboufthe middle of July, in 

 the latitude of St. Louis, some of the individuals begin 

 to acquire wings and continue to issue from the ground 

 until vine-growth ceases in the fall. Having issued 

 from the ground while in the pupa state, they rise in 

 the air and spread to new vine- 

 yards, where they deliver them- 

 selves of their issue in the form 

 of eggs, and then perish. In 

 the course of a fortnight, these 

 eggs which are probably depos- 

 ited in the crevices on the sur- 

 face of the ground, near the 



base of the vine? p r duce the 



sexual individuals, which are 

 born for no other purpose than 

 the reproduction of their kind, 

 and are without means of flight 



[MALE PHYLLOXERA: 

 Ventral View.] 



or of taking food. They are quite active and couple 

 readily. 



Every piece of root having rootlets, taken from an 

 infected vine during August or September, will present 

 a goodly proportion of pupa3, and a glass jar filled with 

 such roots and tightly closed, will furnish daily, for 

 some time, a do^en 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 late summer 



[TYPE RADICICOLA; showing the tubercles by 

 which it is distinguished from Gatlicola.] 



and iall months. We have, therefore, the spectacle of 

 an underground insect possessing the power of contin- 

 ued 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- 



