88 THIRD ANNUAL REPORT OF 



they are hatched they escape from the gall through the orifice on the 

 upper surface of the leaf, which was never entirely closed ; and, ta- 

 king up their abode on the young and tender leaves, in their turn 

 form galls. The mother-louse, after completing her deposit, dies, and 

 the gall which she occupied dries up. There are several generations 

 during the year, and this process goes on as long as the vines put 

 forth fresh leaves. As the galls multiply and the growth of the vine 

 becomes less vigorous, the young lice sometimes so completely cover 

 the upper surface of the newly expanded leaves as not to leave room 

 for them all to form galls. In this event the leaf soon perishes, and 

 the lice perish with it. When two or more lice are stationed closely 

 together they often form but one gall, which accounts for the pres- 

 ence of the several females that are sometimes observed in a single 

 gall. Those leaves which have been badly attacked turn brown or 

 black, and sooner or later fall to the ground, so that the vine may be- 

 come entirely denuded. 



By August the insects generally become so prodigiously multi- 

 plied that they often settle on the tendrils, leaf-stalks, and tender 

 branches, where they form excrescences and gall-like growths, differ- 

 ing only from those on the leaves in such manner as one would natu- 

 rally expect from the difference in the plant tissues. By this time 

 the many natural enemies of the lice begin to play sad havoc with 

 them ; and after the vine has finished its growth, the young lice, find- 

 ing no more succulent and suitable leaves, begin to wander and to seek 

 the roots, so that by the end of September the galls are deserted, and 

 those few remaining on the vines generally become mildewy, and 

 finally turn brown and dry up. Upon the roots the lice attach them- 

 selves singly, or in little groups, and cause by their punctures little 

 swellings and knots, which eventually become rotten. Where vines 

 have been badly affected with the gall, it is difficult to find a perfectly 

 healthy |fibrous root. Strange enough, these lice not only change 

 their residence as winter approaches, from the leaf above ground to 

 the root below ground, just like the - Moor, who, having passed the 

 summer on his roof, gets into his house in the winter; but, Proteus- 

 like. the} 7 change their appearance in shedding their skins, and at the 

 present writing (Nov. 6th) have all become tubercled, as represented 

 at Figure 40, g. 



No doubt the insect passes the winter on the roots in this tuber- 

 cled state, but whether in the spring these tubercled individuals pro- 

 duce winged males and females, which rise in the air, pair, and by de- 

 positing eggs give birth to the apterous females which found the gall- 

 producing colonies; or whether, as spring opens, they lay eggs on 

 the roots, and the young hatching from these eggs crawl up on to the 

 leaves and found those gall-producing colonies, are questions yet to 

 be settled in the life history of our Grape leaf-louse. The former hy- 

 pothesis is, however, by far the most probable, for analogy would lead 

 us to infer that winged males and females must be developed at some 



