LETTER LI 1 1. 



To the same. 



S I have sometimes known you make inquiries 

 about several kinds of insects, I shall here 

 send you an account of one sort which I 

 little expected to have found in this kingdom. 

 I had often observed that one particular 

 part of a vine growing on the walls of my 

 house was covered in the autumn with a 

 black dust-like appearance, on which the flies fed eagerly; 

 and that the shoots and leaves thus affected did not thrive ; 

 nor did the fruit ripen. To this substance I applied my 

 glasses; but could not discover that it had anything to do 

 with animal life, as I at first expected: but, upon a closer 



