36 SIXTH ANNUAL REPORT 



taking the lowest of tlie above figures, the immense prolificacy of the 

 species becomes manifest. Small as the animal is, the product of a 

 single year, even at this low estimate, would encircle the earth over 

 thirty times if placed in a continuous line, each individual touching 

 the end of another. Well it is for us that they are not permitted to 

 multiply in this geometrical ratio! Nevertheless, as summer ad- 

 <vances, they do frequently become prodigiously multiplied, com- 

 pletely covering the leaves with their galls, and settling on the 

 tendrils, leaf-stalks, and tender branches, where they also form knots 

 and rounded excrescences (Fig. 4, e), much resembling those made 

 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 leit are almost always infested with 

 mildew {Botrytis viticola, Berkely), and eventually turn brown and 

 •decay. On the roots, the young lice attach themselves singly or in 

 little groups, and thus hibernate. The male gall-louse has never been 

 seen, and there is every reason to believe that he has no existence. (4) 

 Kor does the female ever acquire wings. Indeed, I can not lay too 

 much stress on the fact that gallcecola 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. (5) I have found it occasionally on 

 all species of the Grape-vine (vifiifera, ripana^ cestivalis, and Za- 

 ■hrusca) cultivated in the Eastern and Middle States, and on the wild 

 cordifolia; but it flourishes only on the liiver-bank grape {ri2)aria)^ 

 •and more especially on the Clinton and Taylor, with their close allies. 

 Thus, while legions of the root-inhabiting type {radicicola) are over- 

 running and devastating the vineyards of France, this gallwcola is 

 almost unknown there, except on such American varieties as it infests 

 with us. A few of its galls have been found at Sorgues, on a variety 

 called Tinto ; and others have been noticed* on vhiifera v\ne% inter- 

 locking infested American vines, or have been produced by purposed 

 contact with the young (/aUoiGola. Similarly, there are many varie- 

 ties, especially of Labrusca^ which, in this country, sutler in the roots, 

 and never show a gall on the leaves. 



The precise conditions which determine the production and multi- 

 iPlication oi gallcecola can not now, if they ever can, be stated ; but it 

 is quite evident that the nature and constitution of the vine are im- 

 portant elements, since such vines as the Herbemont often bear wit- 

 ness, by their leaves covered with abortive galls, to the futile efforts 



