i7 
We have already paid heavily for the introduction of certain 
ticks, such as that ( Margaropus annulatus) of tick fever of cattle 
and the fowl-tick ( Argas pestilis). As regards mosquito-borne 
diseases, both malaria-transmitting mosquitoes (Anophelines) and 
filaria-transmitting ones (Culicines) are to be found near Perth, 
though the former of the two is not common. So far, however, 
we have not the diseases transmitted by either. In the presence 
of the mosquitoes, nevertheless, is seen the possibility of the 
establishment of both malaria and filaria (elephantiasis) in the 
southern parts of Western Australia should persons arrive harbour- 
ing the respective parasites and be bitten by many of the trans- 
mitting mosquitoes. In Brisbane, filarial worms can now be 
found in the blood of a large percentage of the people, the disease 
being transmitted by the local mosquitoes from imported cases 
atjthe beginning. 
PLANTS. 
In the vegetable kingdom we have some most unfortunate 
exotics. The bulbous wire-grass is replacing all herbage in the 
Cannington District. The prickly pear ( Opuntia ) in Queensland 
now covers extensive areas and is costing large sums to eradicate. 
Star-thistles (Centaurea calcitrapa) and Stinkwort cause trouble 
in places. Some of the Queensland rivers have been choked with 
the water-hyacinth. Let me offer a solemn warning to the 
people of Western Australia. Some unscrupulous person has 
already introduced the plant, which has beautiful heads of 
flowers, and the rock-pools at Mount Eliza are full of it (or were 
so when I left the State), and some of the swamps at South 
Perth and in North Perth are simply covered with it. By design 
or accident, it is sure in time to enter various of our rivers and 
reservoirs and there, spreading rapidly, cover them with vegetable 
growth which, decaying in masses and harbouring all kinds of 
life,' would soon render reservoir water undrinkable and rivers 
unnavigable. Imagine Mundaring Reservoir built at such 
enormous cost and on whose supply of water so many depend, 
covered with this growth ! 
CONCLUSION. 
In conclusion, I may say that it has been the endeavour of 
this paper to indicate the very grave dangers that may attend 
inadvertent exotic invasions from parts over sea. I have tried 
to show how some of the ills we now suffer from might have 
been avoided by more carefully excluding from or scrutinizing 
the introduction of certain living things into Australia. And 
I shall feel satisfied if this paper helps in any way to protect us 
in the future, by calling attention to the imperative need of 
thoroughly and scientifically supervising every possible chance 
