Mr. CuRTis's Ohjervatwns on Aphides^ .^5 



was delivered of a young one. Many years before this experiment, 

 with a view to deftroy the Aph'uUs which infefted a plant in my 

 green-houfe, I immerlcd on? evening the whole plant, together 

 with the pot in which it grew, in a tub of water. In the morning 

 I took out the plant, expelling ."ith certainty to find every Apbi* 

 dead ; but to my great furprife they foon appeared alive and well : 

 and thus, in addition to the other extraordinary phaenomcna at- 

 tendant on thefe iafc6ls, we find that they are capable of refilting 

 the efFe6ls of immerfion in water for a great length of time. When 

 taken from the plant on which they feed, and kept under water,, 

 they do not furvive lo long; their ih'uggling in that cafe perhaps 

 exhaufts them fooner. This part of the fubject might be pulhed 

 much further : it is fufFicient for our purpofe to hiive ihown that 

 wet is not fo hurtful to them as is generally imagined. 



Though no mode ot deflroying ylphides will perhaj')s txc^ be de- 

 vifed on a large fcale in the open air by artificial means, we can 

 accomplilli it moll: efFedually when they infeft plants in lloves, 

 green-houfes, and frames, or in any fituation in which we can en- 

 velop them for a certain time in clouds of fmoke. Powders or 

 liquids, however fatal to Aphides, muft ever be ineffe6lual, from the 

 trouble and difficulty of applying them fo that they thall come in 

 contact with thofe infefts, fituated as they ufually are ; but in this 

 refpe6l fmoke has every advantage, it penetrates and pervades their 

 inmoft recelTes. The fmoke of common vegetables, however power- 

 ful, is found to be inadequate to their deftruelion, and hitherto no 

 other than that of tobacco is found to be effectual. That, judi- 

 cioufly applied, completely anfwers the purpofe,\vithout injuring the 

 plant. It moftly happens in well managed houfes that a few plants 

 only are infcfted with Aphides : in fuch a cafe, the fmoking. of the 

 whole houfe is abufmefs of unnecefTarycxpenfe and trouble; and we 

 would recommend to perfons who have large collections to make, ufe 

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