172 The Naturalist in Nicaragua 
its new house full of food. It hollows this out, leaving only 
the hardened shell of the thorn. Strange to say, this treat- 
ment seems to favour the development of the thorn, as it 
increases in size, bulging out towards the base; whilst in my 
plants that were not touched by the ants, the thorns turned 
yellow and dried up into dead but persistent prickles. I am 
not sure, however, that this may not have been due to the 
habitat of the plant not suiting it. 
These ants seem at first sight to lead the happiest of 
existences. Protected by their stings, they fear no foe. 
Habitations full of food are provided for them to commence 
housekeeping with, and cups of nectar and luscious fruits 
await them every day. But there is a reverse to the picture. 
In the dry season on the plains, the acacias cease to grow. 
No young leaves are produced, and the old glands do not 
secrete honey. Then want and hunger overtake the ants 
that have revelled in luxury all the wet season; many of the 
thorns are depopulated, and only a few ants live through the 
season of scarcity. As soon, however, as the first rains set 
in, the trees throw out numerous vigorous shoots, and the 
ants multiply again with astonishing rapidity. 
Both in Brazil and Nicaragua I paid much attention to the 
relation between the presence of honey-secreting glands on 
plants, and the protection the latter secured by the attendance 
of ants attracted by the honey. I found many plants so 
protected; the glands being specially developed on the 
young leaves, and on the sepals of the flowers. Besides the 
bull’s-horn acacias, I, however, only met with two other genera 
of plants that furnished the ants with houses, namely the 
Cecropie and some of the Melastome. I have no doubt that 
there are many others. Thestem of the Cecropia, or trumpet- 
tree, is hollow, and divided into cells by partitions that 
extend across the interior of the hollow trunk. The ants 
gain access by making a hole from the outside, and then 
burrow through the partitions, thus getting the run of the 
whole stem. They do not obtain their food directly from 
the tree, but keep brown scale-insects (Coccid@) in the cells, 
which suck the juices from the tree, and secrete a honey-like 
fluid that exudes from a pore on the back, and is lapped up 
by,the ants. In one cell eggs will be found, in another grubs, 
