176 APHIS. 



sidering the Aphides as the authors of it. That 

 they are capable of producing an appearance ex- 

 actly similar to that of the honey-dew has already 

 been shewn. As far as my own observation has 

 extended, there never exists any honey-dew but 

 where there are Aphides; such however often pass 

 unnoticed, being hid on the under-side of the leaf. 

 Wherever honey-dew is observable about a leaf, 

 Aphides will be found on the under side of the 

 leaf or leaves immediately 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 incontrovertibly 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, it 

 gives to the surface of the bark, foliage, or what- 

 ever it has dropped on, that sx>oty kind of appear- 

 ance which arises from the explosion of gun- 

 powder, which greatly disfigures the foliage, &c. 

 of plants. It looks like and is sometimes mis- 

 taken 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 converted into the same kind of 

 powder." 



" In most seasons the natural enemies of the 

 Aphides are sufficient to keep them in check, and 



