The Bull’s-Horn Thorn Ant 171 
forest, nor are the small ants attending on them found there. 
They seem specially adapted for the tree, and I have seen 
them nowhere else. Besides the Pseudomyrma, I found 
another ant that lives on these acacias; it is a small black 
species of Crematogaster, whose habits appear 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 not near the end, like the Pseudomyrma ; and it is 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 BULL’S-HORN THORN 
the other. The glands on the acacia are also frequented by 
a small species of wasp (Polybia occidentalis). I sowed the 
seeds of the accacia 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 de- 
foliated them, but I have never seen any of the trees out on 
the savannahs that are guarded by the Pseudomyrma touched 
by them, and have no doubt the acacia is protected from 
them by its little warriors. The thorns, when they are first 
developed, are soft, and filled with asweetish, pulpysubstance ; 
so that the ant, when it makes an entrance into them, finds 
