EFFECT OF SETTLEMENT UPON INDIGENOUS VEGETATION. 227 
root crops in general. From the amount of destruction wrought 
in this way, we are able to gauge the amount done to native plants 
whose roots they feed on. I have seen in a single night, a pad- 
dock of one acre completely rooted up by bandicoots. Kangaroo 
rats, too, generally increase in new settlements and must have an 
effect on the flora. | 
Within the past few years, there have been many instances of 
Australian forests decaying, discussed by various authors. Mr. 
R. B. Smyth has already been quoted on the subject, his opinion 
being that the alteration of surface drainage and consequent 
erosion of the ground is responsible for most of the damage. But 
while Iam convinced that much damage is done in this way, I 
have seen some instances where this could not have been the cause, 
and where it must be attributed to an undue increase of some 
animals caused by the alteration of conditions following in the 
wake of settlement. As the following will show, I am not alone 
in this opinion. In a paper by the late Sir William Macleay, an 
account was given of the amazing numbers of Phasmide found 
on Eucalypts at Binda (now Jenolan) Caves by the late Mr. C.S. 
Wilkinson, Government Geologist. The insects were described as 
lying in heaps under the trees, which were completely denuded of 
leaves by them. Such an enormous increase in number of these 
insects must have had some cause, perhaps the decrease of the vari- 
ous birds—Podargus, Dacelo, etc., preying on them.* Mr. A. W. 
Howitt gives an instance of a belt of red gums (Hucalyptus 
rostrata) destroyed by the larve of Urubra lugens, which ate the 
epidermis of the leaves and thus asphyxiated the trees,+ and he 
is also quoted by Sir William Macleay on the subject of a cater- 
pillar very destructive to Eucalyptus tereticornis, the larva being 
that of a species of Orygia.{ Further, in a paper on ‘‘Some causes. 
of decay of Australian forests” the late Rev. Peter Macpherson, 
summarises the alleged causes as (1) Flat wet lands, (2) Seasons 
* Proc. Linn. Soc. of N.S. Wales, Vol. vi., p. 536. 
+ Trans. Roy. Soc. of Victoria, Vol. 11., p. 81. 
{ Proc. Linn. Soe. of N.S. Wales, Vol. vit., p. 344. 
