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IV. Ohfervafions on Aphides^ ch'iefiy intended tv //:ow that they are the 

 principal Caufe of Blights in Plants, and the fak Caufc of the Honey- 

 Deiv. By the late Mr, William Curfis, F. L. S. ■ • • - ^ 



Read May 6, 1800. 



X H E Jpbist or Blighter, as we now for the firll time venture to 

 call it, from its being the moft general caufe of what are termed 

 blights in plants, forms a highly interefting tribe of infects. In 

 point of number, the individuals of the feveral fpecies compofing it 

 furpafs thofe of any other genus in this country*. 



Thefe infects live entirely on vegetables. The lofticft tree is no 

 kfs liable to their attacks than the moft humble plant. They prefer 

 the young fhoots on account of their tendernefs, and on this prin- 

 ciple often infinuate themfelves into the very heart of the plant, and 

 do irreparable mifchief before they are difcovered. But for the moft 

 part they befct the foliage, and are always found on the under fide 

 of the leaf, which they prefer, not only on account of its being the 

 iTioft tender, but as it affords them protection from the weather, and 

 various injuries to which they would otherwife be expofcd. Some- 

 times the root is the object of their choice, which, from the nature 

 of thefe infects, one would not a priori Qx^e€t ; yet have I feen the 

 roots of lettuces thickly befet by them, and the whole crop rendered 

 fickly and of little value : but fuch iuftanccs are rare. They rarely 



* Reaumur, confidering each Aphis as bringing forth ninety young, calculates that in 

 £vc generations the produce from a fingle one would be five thoufand nine hundred and 

 iour million nine hundred tlioufand. 



L 2 ^lio 



