224 THE NATURAL HISTORY 



that they can subsist longer is undeniable. The second is, 

 that this uncommon event, as it was owing to the loss 

 of the first brood, so it corroborates my former remark, 

 that swifts breed regularly but once ; since, was the con- 

 trary the case, the occurrence above could neither be new 

 nor rare, 



P.S. One swift was seen at Lyndon, in the county 

 of Rutland, in 1782, so late as the third of September 



LETTER LIII 



TO THE HONOURABLE DAINES BARRINGTON 



As 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 examination behind 

 the larger boughs, we were surprised to find that they were 

 coated over with husky shells, from whose sides proceeded 

 a cotton-like substance, surrounding a multitude of eggs. 

 This curious and uncommon production put me upon 

 recollecting what I have heard and read concerning the 

 coccus vitis viniferae of Linnaeus, which, in the south of 

 Europe, infests many vines, and is an horrid and loathsome 

 pest. As soon as I had turned to the accounts given of 

 this insect, I saw at once that it swarmed on my vine ; 

 and did not appear to have been at all checked by the 

 preceding winter, which had been uncommonly severe. 

 Not being then at all aware that it had anything to 



