young, secretes a honey-like fluid. Of this the ants are 
very fond, and they are constantly running about from one 
gland to another to sip up the honey as it is secreted. 
But this is not all; there is a still more wonderful pro- 
vision of more solid food. At the end of each leaflet there 
is, when the leaf first unfolds, a little yellow, pear-shaped 
body, united by a point, and the ants are then continually 
employed going from one to another examining them. 
When an ant finds one sufficiently advanced, it bites its 
small point of attachment; then, bending it down, it 
breaks it off, and bears it away to the nest. As these 
ripen successively, the ants are kept about the young leaf 
for some time after it unfolds ; and no caterpillar or larger 
animal could attempt to injure them without being 
attacked by the little warriors. The fruit-like bodies are 
about ,/, in. long, and are about 4 of the size of the 
ants ; so that the ant bearing one away is as heavily laden 
as a man bearing a large bunch of plantains. I think 
these facts show that the ants are really kept by the acacia 
as a standing army, to protect its leaves from the attacks 
of herbivorous mammals and insects, 
‘The bull’s-horn thorn does not grow at the mines in 
the forest, nor are the small ants attending them found 
there. They seem specially adapted for the tree, and I 
have seen them nowhere else. Besides the Pseudomyrma, 
another ant lives on these Acacias; it is a small black 
species of Crematogaster, whose habits seem to be rather 
different from those of Pseudomyrma. It makes the holes 
of entrance to the thorns near the centre of one of each 
pair; and itis not so active as that species. It is also 
rather scarce; but when it does occur it occupies the 
whole tree, to the exclusion of the other. The glands on 
the Acacia are also frequented by a small species of wasp 
Polybia occidentalis). I sowed the seeds of the Acacia in 
my garden, and reared some young plants. Ants of many 
kinds were numerous ; but none of them took to the thorns 
for shelter, nor the glands and fruit-like bodies for food ; 
for, as I have already mentioned, the species that attend 
on the thorns are not found in the forest. The leaf-cutting 
ants attacked the young plants and defoliated them ; but 
I have never seen any of the trees out on the savannahs 
that are guarded by the Pseudomyrma touched by them, 
