64 



SIXTH ANNUAL REPORT 



assert, and I think the facts here set forth will bear out the assertion, 

 that our vines languish or die more often from Phylloxera than from 

 any other cause, whether in connection with or entirely independent 

 of cryptogamic plant growth. 



THE AMERICAN OAK PHYLLOXERA— PAyi/o^-era Rileyl Lichtn. 



There are several described. and undescribed species of Phyl- 

 loxera in this country, most of them inhabiting leaf-galls made on our 

 r*'is- 18 ] different hickories. The species herewith 



figured is the only external feeder known in 

 America, and is briefly alluded to in this con- 

 nection to show that, as with the Grape Phyl- 

 loxera, it does not need a "wintef egg" to 

 enable it to hibernate, but passes the winter 

 in the larva state, (as at Fig. 19), firmly at- 

 tached to the tender bark of the younger 

 ' twigs and thus braving all the vicissitudes and 

 inclemencies of that season. In the summer 

 ^'"wingeTtMer^VimW^^^ ^® fouud ou the Under surface of the leaves 



'4(^^^S^'''''''^'"'''of\hG White and Post oaks, in the wingless 

 female state of all sizes. Soon after it is born it inserts its beak into the 

 leaf-tissue, and becomes more or less stationary. It causes no swelling 

 of the leaf, but a yellow circular spot (Fig. IS, d) somewhat larger 

 than its own body and showing most plainly on the upper surface. The 

 eggs are laid singly around the louse, and the process of partheno- 

 [i^'is- 1^] genetic reproduction goes on for several 



generations, as in the Grape Phylloxera. 

 By about the end of August, when these 

 lice and their eggs are often very numer- 

 ous, and when the speckled and often 

 ^"^ withered appearance of the leaf easily 

 ''"'veXfi'^vi^^^^^^^^ presence, the winged indi- 



"Skofsamlf''''"'^"''"''''^'"''' viduals begin to appear. 

 This species is at once distinguished from all other American 

 species, so far known, by its slender form and small size, but particu- 

 larly by the long tubercles of the larger apterous individuals, and of 

 the pnpfB (Fig, 18, a.) Otherwise it greatly resembles the Grape 

 Phylloxera in color, and in the different forms it assumes, and for 

 more detailed descriptions I refer the reader to the appendix. (25.) In 

 habit and general appearance it very closely resembles the European 

 Oak Phylloxera; but differs remarkably in its winter habit from what 



