6 THE POPULAR SCIENCE MONTHLY, 



they lose their globular tips and become more or less worn with age. 

 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 the tomentose nature of 

 these leaves affords, and commence pumping up and appropriating 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 mi- 

 croscope—is sharp, and easily run under the parenchyma of the leaf. 

 Its puncture causes a curious change in the tissues of the leaf, the 



Fig. 



Type Gall^ecola.— a, &, Bewly-hatched lai-va, ventral and dorsal view : <?, egg; d. section of gall ; 

 e^ swelliniT of tendril ; /, g, A, mother frcall-louse— lateral, dorsal, and ventral views ; 2, her an- 

 tenna ; j, her two-jointed tarsus. Natural sizes indicated at sides. 



growth being so stimulated that the under 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 premature death of the louse, 

 or other cause, the gall becomes abortive before being completed, then 

 the circle of thickened down or fuzz enlarges with the expansion of 

 the leaf, and remains (Fig. 2, c) to tell the tale of the futile eflbrt. 

 Otherwise, in a few days the gall is formed, and the inheld louse, 

 which, while eating its way into house and home, was also growing 

 apace, begins a parthenogenetic maternity by the deposition of fertile 

 eggs, as her immediate parent had done before. She increases in bulk 

 with pregnancy, and one eg^ 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 qq,^ brings 

 forth a fertile female, which soon becomes wonderfully prolific. The 



