56 



little oval, hexapod beings, which differ from their mother in their bright yellow 

 colour and more perfect legs and antenna?, the tarsi being furnished with long, 

 pliant hairs, terminating in a more or less distinct globule. In hatching, the eggs 

 split longitudinally from tbe anterior end, and the young louse whose pale yellow is 

 in strong contrast with the more dusky colour of the egg-shell, escapes in the course 

 of two minutes. Issuing from the mouth of the gall, these young lice scatter over the vine, 

 most of them finding their way to the tender terminal leaves, where they settle in the downy 

 bed which thetomentose nature of these leaves affords, and commence pumping up and appropriat- 

 ing the sap. The tongue-sheath is blunt and heavy, but the tongue proper — consisting of 

 three brown, elastic and wiry filaments, which, united, make so fine a thread as scarcely to be 

 visible with the strongest microscope — is sharp, and easily run under the parenchyma of the 



leaf. Its puncture causes a curious change 

 in the tissues of the leaf, the growth being 

 so stimulated that the tinder side bulges 

 and thickens, while the down on the upper 

 side increases in a circle around the louse, 

 and finally hides and covers it as it recedes 

 more and more within the deepening cavity. 

 Sometimes the lice are so crowded that two 

 occupy the same gall. If, from the prema- 

 ture death of the louse, or other cause, the 

 gall becomes abortive before being com- 

 pleted, then the circle of thickened down 

 or fuzz enlarges with the expansion of the 

 leaf, and remains (Fig. 43, c) to tell the 

 tale of the futile effort. Otherwise, in a 

 few days the gall is formed, and the inheld 

 ^ A louse, which, while eating its way into 



TrPE G4LL/EC01A :-«, b, newly-hatched larva, ventral and dorsal house and home, was also growing apace, 



^^ew; c, egg ; d, section of gall; e sweUing of tendril; /, g h, begins a parthcnogenetic maternity by the 



mother gall-louse — lateral, dorsal and ventral views ; t, her anten- , ^ . . ^ « , 9 ., i • 



na;j, her two jointed tarsus. Natural sizes indicated at .sides. depr SltlOn 01 the fertile CggS, aS her imme- 



diate parent had done before. She increases in bulk with pregnancy, and one egg follows 

 another in quick succession, until the gall is crowded. The mother dies and shrivels, and the 

 young, as they hatch, issue and found new galls. This process continues during the summer 

 until the fifth or sixth generation. Every egg brings forth a fertile female, which soon be- 

 comes wonderfully prolific. The number of eggs found in a single gall averages about 200 ; 

 yet it will sometimes reach as many as 500, and, if Dr. Shimer's observations can be relied on, 

 it may even reach 5,000. I have never found any such number myself; but, even supposing 

 there are but five generations during the year, and taking the lowest of the above figures, the 

 immense prolificacy of the species becomes manifest. As summer advances they frequently 

 completely cover the leaves with their galls, and settle on the tendrils, leaf-stalks and tender 

 branches, where they also form knots and rounded excrescences (Fig. 43, e) much resembling 

 those on the roots. In such a case, the vine loses its leaves prematurely, usually, however, 

 the natural enemies of the louse seriously reduce its numbers by the time the vine ceases its 

 growth in the fall, and the few remaining lice, finding no more succulent and suitable leaves, 

 seek the roots. Thus by the end of September, the galls are mostly deserted, and those 

 which are left are almost always infested with mildew, and eventually turn brown and decay. 

 On the roots the young lice attach themselves singly or in little groups and thus hibernate. 

 The male louse has never been seen, nor does the female ever acquire wings. Indeed, too 

 much stress cannot be laid on the fact that GaUwcola 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, compared with the other type, but trifling damage. It 

 has been found occasionally by Mr. Riley on all species of the grape-vine {vinifera, riparia, 

 a'stiralis and Lubrusca) cultivated in the Eastern and Middle States, and on the wild cordifolia ; 

 but it flourishes only on the river-bank grape (riparhi), and more especially on the Clinton 

 and Taylor, with their close allies. Thus while legions of the root-inhabiting type [radicicola) 

 are overrunning and devasting the vineyard.s of France, this one is almost unknown there 

 except on such American varieties as it infests with us." 



