■66 FOURTH ANNUAL REPORT OF 



<-aii manage to fly through the air to any great distance; and those who 

 have not witnessed them in flight are very apt to underrate their power of 

 volitation. There is a conical gall very connnon on the upper surface of the 

 leaves of our Shell-bark hickories. This gall is made by a louse very closely 

 allied to our GrajDe-leaf gall-louse and was named Phylloxera carycefolice 

 by Dr. Fitch. * This louse occurs abundantly in the winged form, and fur- 

 nishes an excellent illustration of the power of the insects of this genus to 

 fly. Let any one watch these winged gall-lice, as they issue, during some 

 warm day in June, from the fimbriated mouth of their gall, and he will be 

 •■etruek with astonishment at the facility and power with which they fly ofl". 

 They are no sooner out of the gall than the wings commence to vibrate so 

 ■■&S to become invisible, and the insect suddenly darts away with wonderful 

 force. They must likewise, often be carried great distances by the wind. 



Again, it would at first sight seem almost impossible for the female to de- 

 2)osit her loose eggs which have no viscous proijerty, ujDon a swaying leaf; 

 but this very feat is accomplished by another little louse of the same genus,f 

 which may be found dej^ositing its eggs all through the summer months, 

 on the under side of the leaves of our young Post oaks. 



PROBABLE REASON WHY ITS INJURIES ARE GREATER IN EUROPE THAN WITH US. 



It is a well recognized fact among careful observers, that in the natural 

 «tate there is greater harmony between the fauna and flora of a country 

 than in the more artificial state that civilized man induces by cultivation. 

 Through a long series of ages, the sjiecies least able to contend in the. 

 struggle for life, "go to the wall," until at last, b}^ a process of elimination, 

 the balance is struck and we find the animal and plant world well adapted 

 and adjusted to each other. For this reason the native vines which now 

 flourish in this country are those which have fought the long battle in the 

 pasr and have best resisted the enemy. They are, in short, best adapted to 

 the circumstances, and by their more vigorous nature resist the hypertrophy 

 •of the bark caused by the punctures of the lice, and form new bark under 

 It. The European vines, on the contrarj^, are not only of a more highly 

 improved and tender character, but have not been accustomed to the dis- 

 ease. They consequently succumb more readily, on the same jirincijile that 

 anany diseases that are comparatively harmless among civilized nations, 

 acquire greater virulency and play fearful havoc when introduced among 

 savage, or hitherto uncontaminated peoples. 



There may be other reasons, such as the different modes of culture and 

 ■difl'erence of soil ; for in the French districts so badl}- afl'ected the vines are 

 either grown with a single stake or no stake at all, and their soil is gener- 

 ally much poorer than ours. In America, also, we know that there arc sev- 

 eral natural enemies of the louse, and these checks have, in all likelihood, 

 never been imported into Europe with their prey. That the louse will in 



*Jiep. III. §166. 



t This is a species of Phijlloxcra which is yet uurtescribed, but which M. J. Lichtenstein proposes 

 K) call Ph. Rileyi. It infests the leaves of our Post oak very much in the same manner as the European 

 Ph. qiHvcus infests their oaks— causing a similarly pale speckled appearance of the ui)per side of the 

 leaves. It dilTers from all described species in the great length and prominence of the tubercles. 



