If 





44 



DISEASES 



Sect. XIV. 3. 2. 



multiplied by fifty, and that produa again multiplied by fifty nine 

 times would ^ive the product of one egg only in countlefs millions; 



to w 



hich muft be added the innumerable eggs laid by the tenth ge- 



neration for the renovation of their progeny in the enfuing fpring. 



Their pun6lures of the leaves of peach and nedarine trees in the 

 vernal months, and of cherry, plum, and currant trees in the fum- 

 mer, produce a fwelling and elevation of the cuticle of the leaf on its 

 upper fide, and a confequent curling of it with its upper furface out- 

 wards, which terminates in a deftrudion of it to the great injury of 

 the tree, and frequently to the death of it ; while the leaves of the 

 nut-trees, mentioned above, in No. i. 7. of this Se£lion, appeared to 

 be but little injured by them, though fifty or a hundred of thele in- 

 fers were feen under every leaf about Midfummer, both before and 



after their affufion with the honey-dew. 



From Dr. Richardfon's account the aphifes on the rofe-tree ap- 

 peared in February, when the weather happened to be warm, from 

 fmall black oval eggs ; which were depofited on the laft year's (hoots 



1 ; and that, when the weather became colder, great num- 

 bers of them periflied, by which circumflance 

 fome years almoft freed from them. 



autum 



the rofe 



They came to thdr full growth 



before April, and after having 



twice cad off their exuviae, every one of them produced about fifty 



into the world backwards, and ad- 



youn 



of which came 



hercd fometime to th 



of the parent by their mouths or fore 



part 



as (hewn in a magnified ftate at fig. 2. plate IX ; and were 



length fet down on fome tender (hoots of the plant, and came to ma- 

 turity in about ten days, calling off their coats two, three, or four 



times. 



The ninth generation in Odober confifted of males as well as fe- 

 males, which were feen to cohabit ; and the eggs produced by their 

 intercourfe, he alTerts, were depofited generally near the new buds, 

 or on other parts of the twigs of the trees, which they polfefled 



8 



Thefe 



-- 



i 



