INSECTS AND DISEASE. 
By Dr. A. JEFFERIS TURNER, 
M.D., Lonp., D.p.o., Cams. 
A Paper read before the Royal Society of Queensland, 
on January 27th, 1908. 
‘CasTING about for some topic on which to address you, 
it has occurred to me to chose for my subject the relation- 
ship between insects and disease, or insects as disease 
carriers. I must, however, disclaim any attempt to treat 
this subject in an exhaustive fashion. Of recent years, 
this department of science has grown too large to be 
adequately dealt with in my time-limit. Instead of 
attempting a bare summary of the whole ground, I think it 
will be more interesting and instructive to select two or 
three of the better-known instances and to consider them 
more thoroughly. 
Insects may convey disease in two ways. Firstly, 
they may act as occasional bearers of disease-organisms, 
which may happen to adhere to the outside of their bodies. 
In this way they may become fortuitous carriers of diseases, 
which are by no means entirely dependent upon them for 
propagation, but whose spread may under favourable 
conditions, be greatly increased by insect agency. There is 
no doubt, for example, that the common housefly may be, 
and is, a disease carrier. 
When the late Mr. Darwin was investigating the 
methods by which plants might be conveyed to oceanic 
islands, apart from human agency, it occurred to him to 
examine the legs of birds. He found that it was not un- 
common for small particles of earth to be found adhering 
to their legs and feet, and that this earth sometimes con- 
tained seeds, which could germinate and produce plants. 
