170 The Naturalist in Nicaragua 
with jaws and sting. They sting severely, raising a little 
white lump that does not disappear in less than twenty-four 
hours. 
These ants form a most efficient standing army for the 
plant, which prevents not only the mammalia from browsing 
on the leaves, but delivers it from the attacks of a much 
more dangerous enemy—the leaf-cutting ants. For these 
services the ants are not only securely housed by the plant, 
but are provided with a bountiful supply of food, and to 
secure their attendance at the right time and place, the food 
is so arranged and distributed as to effect that object with 
wonderful perfection. The leaves are bi-pinnate. At the 
base of each pair of leaflets, on the mid-rib, is a crater-formed 
gland, which, when the leaves are young, secretes a honey- 
like liquid. 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 provision of more solid food. At the 
end of each of.the small divisions of the compound leaflet 
there is, when the leaf first unfolds, a little yellow fruit-like 
body united by a point at its base to the end of the pinnule. 
Examined through a microscope, this little appendage looks 
like a golden pear. When the leaf first unfolds, the little 
pears are not quite ripe, and the ants are continually employed 
going from one to another, examining them. When an ant 
finds one sufficiently advanced, it bites the small point of 
attachment; then, bending down the fruit-like body, it 
breaks it off and bears it away in triumph to the nest. All 
the fruit-like bodies do not ripen at once, but successively, 
so that the ants are kept about the young leaf for some time 
after it unfolds. Thus the young leaf is always guarded by 
the ants; and no caterpillar or larger animal could attempt 
to injure them without being attacked by the little warriors. 
The fruit-like bodies are about one-twelfth of an inch long, 
and are about one-third of the size of the ants; so that an 
ant carrying 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 
