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IV. Ol^crvai'iovs on j^phides, chiefly inicmkJ to JI:ow that they are the 

 principal Caufe of Blights in Plants, and the fole daufc of the Honeys- 

 Dew. By the laic Mr. William Curtis, F. L. S. 



Read May 6, i8oo. 



X H E Jphis, or Blighter, as we now for the firft time venture to 

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

 blights in plants, forms a^ highly intcrefting tribe of infedls. In 

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

 lurpafs thole of any other genus in this country*. 



Thefe infers live entirely on vegetables. The loftiefl; tree is no 

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

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

 ciple often infmuatc themfclvcs into the very heart of the plant, and 

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

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

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

 moft tender, but as it affords them proteftion from the weather, and 

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

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

 of thefe infedts, one would not H priori expeft ; yet have I feen the 

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

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



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

 fhe generations the produce from a Gngle one would be five thoufand nine hundred and 

 feur million nine hundred tltoufand. 



L 2 alfc 



