174 The Naturalist in Nicaragua 
Para. Every pouch was occupied by a nest of small black 
ants, and if the leaf was shaken ever so little, they would 
rush out and scour all over it in search of the aggressor. I 
must have tested some hundreds of leaves, and never shook 
one without the ants coming out, excepting on one sickly- 
looking plant at Para. In many of the pouches I noticed 
the eggs and young ants, and in some I saw a few dark- 
coloured Coccide or aphides; but my attention had not been 
at that time directed to the latter as supplying the ants with 
food, and I did not examine a sufficient number of pouches 
to determine whether they were constant occupants of the 
nests or not. My subsequent experience with the Cecropia 
trees would lead me to expect that they were. Ifso, we have 
an instance of two insects and a plant living together, and 
all benefiting by the companionship. The leaves of the plant 
are guarded by the ants, the ants are provided with houses 
by the plant, and food by the Coccide or aphides, and the 
latter are effectually protected by the ants in their common 
habitation. 
Amongst the numerous plants that do not provide houses, 
but attract ants to their leaves and flower-buds by means of 
glands secreting a honey-like liquid, are many epiphytal 
orchids, and I think all the species of Passzflora. I had the 
common red passion-flower growing over the front of my 
verandah, where it was continually under my notice. It had 
honey-secreting glands on its young leaves and on the sepals 
of the flower-buds. For two years I noticed that the glands 
were constantly attended by a small ant (Pherzdole), and, 
night and day, every young leaf and every flower-bud had a 
few on them. They did not sting, but attacked and bit my 
finger when I touched the plant. I have no doubt that the 
primary object of these honey-glands is to attract the ants, 
and keep them about the most tender and vulnerable parts 
of the plant, to prevent them being injured; and I further 
believe that one of the principal enemies that they serve to 
guard against in tropical America is the leaf-cutting ant, as 
I have observed that the latter are very much afraid of the 
small black ants. 
On the third year after I had noticed the attendance of 
the ants on my passion-flower, I found that the glands were 
not so well looked after as before, and soon discovered that a 
