OF THE STATE ENTOISIOLOGIST. 3T 



the lice sometimes persist in making to build in uncongenial places. 

 Yet other elements come into play, and nothing strikes the observer 

 as more curious and puzzling than the transitory nature of these galls, 

 and the manner in which they are found — now on one variety, now 

 on another. (6) 



I was formerly inclined to believe that (/allwaola was a necessary 

 I)hase in the annual cycle of the insect's mutations: in other words, 

 that it was essential to the continuance of the species, and was pro- 

 bably the product of the egg laid by the winged and impregnated 

 female. On this hypothesis I imagined that f/allcecola was probably 

 the invariable precursor«of radloicola in an uninfested vineyard, and 

 that, if galls were not allowed to develop in such a vineyard, it would 

 not suffer from root-lice. More extensive experience has satisfied me- 

 that the hypothesis is essentially erroneous, and that, while the first 

 galls may sometimes by produced by lice hatched from the few egg& 

 deposited above-ground by the winged female, they are more often 

 formed by young lice hatched on the roots, and which, wandering 

 away from their earthy recesses, are fortunate enough to find suitable 

 leaf conditions. It is barely possible that under certain circum- 

 stances, as, for instance, on our wild vines, where the soil around the 

 rocts is hard and compact, gallmcola may become more persistent, 

 and pass through all the phases belonging to the species without 

 descending to the roots — the eggs wintering on the ground, or the- 

 young under the loose bark, or upon the canes. For a somewhat 

 similar state of things actually takes place with another plant-louse 

 { Eriosoma 2)yri,^'\tc\\^) which in the Western United States normally 

 inhabits the roots of our apple trees, and only exceptionally the 

 branches ; while in the moister Atlantic States, and in England and 

 moister parts of Europe, where it was introduced from this country, 

 it normally infests the branches, and more exceptionally the roots.. 

 But there are no facts yet known to prove such to be the case with 

 the Grape Phylloxera, even on our wild vines, and I do not believe 

 that it ever is the case in our cultivated vineyards. 



As already indicated, the autumnal individuals of gallaioola 

 descend to the roots, and there hibernate. There is every reason to- 

 believe also that, throughout the summer, some of the young lice 

 hatched in the galls are passing on to the roots; as, considering their 

 size, they are great travelers, and show a strong predisposition to drop,, 

 their natural lightness, as in the case of the young Cicada^ and of 

 other insects which hatch above but live under ground, enabling them< 

 thus to reach the earth with ease and safety. At all events, I know,, 

 from experiment, that the young gallacola^ if confined to vines on 

 which they do not normally, and perhaps can not, form galls, will, in 



