142 Proceedings of the Royal Society 
often the whole of the trees of a forest, some idea will be formed of 
the magnitude of the operations of these insects and the extent of 
their influence upon the soil which they are thus ceaselessly trans- 
porting from underneath the ground. 
In travelling through the great forests of the Rocky Mountains 
or of the Western States, the broken branches and fallen trunks 
strewing the ground breast-high with all sorts of decaying litter 
frequently make locomotion impossible. But in an African forest 
not a fallen branch is seen. One is struck at first at a certain clean 
look about the great forests of the interior, a novel and unaccount- 
able cleanness, as if the forest-bed was carefully swept and dusted 
daily by unseen elves. And so, indeed, it is. Scavengers of a 
hundred kinds remove decaying animal matter — from the carcase of 
the fallen elephant to the broken wing of a knat — eating it, or 
carrying it out of sight, and burying it in the deodorising earth. 
And these countless millions of termites perform a similar function 
for the vegetable world, making away with all plants and trees, all 
stems, twigs, and tissues, the moment the finger of decay strikes the 
signal. Constantly in these woods one conies across what appears 
to be sticks and branches and bundles of faggots, but when closely 
examined they are seen to be mere casts in mud. From these 
hollow tubes, which preserve the original form of the branch down 
to the minutest knot or fork, the ligneous tissue is often entirely 
removed, while others are met with in all stages of demolition. In 
attacking a small branch the insects start apparently from two 
centres. One company attacks the inner bark, which is the favourite 
morsel, leaving the coarse outer bark untouched, or more usually 
replacing it with grains of earth atom by atom as they eat it away. 
The inner bark is gnawed off likewise as they go along, but the 
woody tissue beneath is allowed to remain to form a protective 
sheath for the second company who begin work at the centre. This 
second contingent eats its way outward and onward, leaving a thin 
tube of the outer wood to the last as props to the mine till they have 
finished the main excavation. When a fallen trunk lying upon the 
ground is the object of attack, the outer cylinder is frequently left 
quite intact, and it is only when one tries to drag it off to his camp- 
fire that he finds he is dealing with a mere hollow tube a few lines 
in thickness filled up with mud. 
