APHIS. 
176 
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 sooty kind of ajppear- 
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 
