86 



the European leaf mite— a supposition in favor of which I shall 

 adduce some further proof. It is worthy of remark that upon even 

 the worst infested plants at Normal the youngest or smallest leaves 

 were usually quite uninjured. 



This same mite was subsequently found by my assistant, Mr. 

 Garman, upon wild grapes in Southern Illinois, producing upon the 

 leaves there an identical deformity. It seems extremely improbable 

 that the European species could have been conveyed to this coun- 

 try and have become so wide spread as to reach the wild vines in 

 forests without having hitherto attracted attention in vineyards ; and 

 I am consequently inclined to believe that the vineyard mite of 

 America has spread in the reverse direction— that it is a native 

 species probably belonging to our wild vines, and has from them 

 entered our vineyards. 



Indeed microscopic study of the mite itself discovers some minor 

 points in which it disagrees with the figures and descriptions of the 

 European Phytoptus vitis. The body is less strictly cylindrical, 

 and the lateral branches of the tarsal plume are less numerous. 

 The descriptions of the European forms by Landois and Briosi are 

 however so inconsistent with each other (the original description of 

 Landois giving, for example, one hundred and twenty as the num- 

 ber of abdominal rings, and that of Briosi from sixty to sixty-six)' 

 that it is impossible to make an intelligent comparison of our form 

 with theirs without authentic specimens. I have consequently treated 

 our species under the old specific name. 



The specimens examined by me varied in length from .45 to .64 

 of an inch, and in greatest diameter from .014 to .019 of an inch. 

 The body is broadest immediately behind the legs and thence tapers 

 regularly, as seen from above, to the posterior extremity. The rings 

 number about sixty-five ; the tarsal plume has certainly but four 

 lateral filaments, and not five, as reported for PJiytoptus vitis by both 

 Briosi and Landois. 



Plant diseases due to Phytopti have hitherto been controlled only 

 by the use of sulphur, the method being described in my Eirst Pie- 

 port, page 142. As such applications are already in use for fungus 

 affections of the grape leaf, they will doubtless be found conveniently 

 applicable for Phytopti in the vineyard. 



