THE GRAPE PHYLLOXERA, 7 



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 im- 

 mense prolificacy of the species becomes manifest. Small as the ani- 

 mal 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 advances, they do frequently become prodigiously multi- 

 plied, completely 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. 3, e), much resembling those 

 made on the roots. In such a case, the vine loses its leaves prema- 

 turely. 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 tfie end of September, the galls are 

 mostly deserted, and those which are left 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 exist- 

 ence. Nor does the female ever acquire wings. Indeed, I cannot lay 

 too much stress on the fact that galloecola 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. I have found it occa- 

 sionally on all species of the Grape-vine {vinifera^ riparia^ cestivalis^ 

 and Labrusca) cultivated in the Eastern and Middle States, and on 

 the wild Cordifolia ; but it flourishes only on the River-bank grape 

 {riparia)^ and more especially on the Clinton and Taylor, with their 

 close allies. Thus, while legions of the root-inhabiting type [radici- 

 cola) are overrunning and devastating the vineyards of France, this 

 galkecola 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 vinifera 

 vines interlocking infested American vines, or have been produced by 

 purposed contact with the young gallcBCola. Similarly, there are 

 many varieties, especially of Lahrusca^ which, in this country, sufier 

 in the roots, and never show a gall on the leaves. 



The precise conditions which determine the production and multi- 

 plication of galloecola cannot 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 

 ^ " Practical Entomologist," vol. i., p. lY. 



