22 ON THE DECADENCE OF AUSTRALIAN FORESTS. 
swarm on the manna gum (Eucalyptus viminalis), and 
feed upon its leaves to such an extent that after a few 
weeks scarcely a perfect leaf can be found; and if the 
opossum theory is to be seriously discussed, surely the 
claim of these insignificant agents to be responsible for 
the work of destruction ought not to be overlooked. 
In considering this matter, however, I have attempted to 
account for the changes which have been going on 
without invoking the assistance of either opossums, 
grubs, or beetles, and in doing so will perhaps expose 
myself to the derision of those gentlemen who have advo- 
cated their claims. Still I believe the question will be 
satisfactorily settled without such adventitious aid; and if 
I have been able to suggest anything which will help other 
inguirers on to the right track, this paper will not have been 
written in vain. 
In conclusion, I would point out that if the theory I have 
advanced in explanation of the decadence of Australian 
forests is a sound one, as applied to the localities with 
which I am familiar, subject to certain modification on 
account of soil, climate, and general treatment of the 
country, it would be equally sound in other districts where 
the trees have sickened and died as they have done in 
many parts of New England. 
