NATURAL HISTORY. 



841 



" it fell upon, and the swarms 

 *' of insects this matter attracted, 

 <' first led me to imagine that the 

 " honey-dew of plants was no other 

 «' than this secretion, which farther 

 ^' observation has since fully con- 

 " firmed. Others have considered 

 " it as an exudation from the plant 

 *' itself. Of the former opinion we 

 *' find the rev. Mr. White, one of 

 *' the latest writers on natural his- 

 " tory that has noticed this sub- 

 "ject. But that it neither falls 

 '' from the atmosphere, nor issues 

 " from the plant itself, is easily de- 

 " monstrated. If it fell from the 

 *' atmosphere, it would cover every 

 <' thing indiscriminately, whereas 

 " we never find it but on certain 

 " living plants and trees. We find 

 "it also on plants in stoves, and 

 " green.houses covered with glass. 

 " If it exuded from the plant, it 

 " would appear on all the leaves 

 *' generally and uniformly ; whereas 

 *' its appearance is extremely irre- 

 *' gular, not alike on any two leaves 

 " of the same tree or plant, some 

 " having none of it, and others being 

 " covered with it but partially. But 

 *■ the phajnomena of the honey- 

 " dew, with all their variations, are 

 " easily accounted for by consider- 

 *' ing the aphides as the authors of it. 

 *' I'hat they are capable of pro- 

 *' ducing an appearance exactly 

 *' similar to that of the honey-dew 

 *' has already been shewn. As far 

 " as my own observation has ex- 

 *' tended, there never exists any 

 *' honey-dew but where there arc 

 *' aphides ; such however often pass 

 , '' unnoticed, being hid on the under 

 *' side of the leaf. Wherever honey- 

 *' dew is observable about a leaf, 

 *' ai»Jiides will be found on the un- 

 *' der side of the leaf or leaves im- 

 *' mediately above it, and under no 



" other circumstances whatever. 

 " If by accident any thing should 

 " intervene between the aphides 

 " and the leaf next between them, 

 " there will be no honey-dew on 

 " that leaf. Thus then we flatter 

 " ourselves to have incontrovcrtibly 

 " proved that the aphides are the 

 " true and only source of the honey- 

 " dew." 



" We have found that where the 

 " saccharine substance has dropped 

 " from aphides for a length of 

 " time, as from the aphis salicis in 

 "particular, it2;ives to the surface 

 " of the bark, foliage, or whatever 

 '>'• it has dropped on, that sooty kind 

 " of appearance which arises from 

 " the explosion of gunpowder, 

 "which greatly disfigures the foli- 

 " age, itc. of plants. It looks like 

 " and is sometimes mistaken for a 

 " kind of black mildew. We have 

 " some grounds for believing that a 

 " saccharine substance similar to 

 " that of the aphis drops from the 

 " coccus also, and is finally con- 

 " verted into the same kind of 

 " powder." 



" In most seasons the natural 

 " enemies of' the aphides aresuffici- 

 " cut to keep them in check, and 

 " to prevent them from doing any 

 " essential injury to plants in the 

 " open air. But seasons sometimes 

 " occur, very irregularly indeed, 

 " on an average, perhaps once in 

 " four or six years, in which they 

 " are multiplied to such an excess, 

 " that tile usual means of diminu- 

 " tion fail in preventing them from 

 " doing irreparable injury to certain 

 " crops. In severe winters we have 

 " no doubt (hat aphides arc very 

 " considerably diminished: in very 

 " mild winters we know they are 

 " very considerably increased ; for 

 " they not only exist during such 



" seasons 



