Ridley .— Symbiosis of Ants and Plants . 
469 
Platycerium biforme, Bl. 
This fern has three sets of fronds, viz. large and broad erect ones which S 
form the large nest, from below which hang the branched pendant fronds 
which give the plant its common name, and among which are those which 
bear the kidney-shaped spore-producing fronds. 
The large erect fronds form a kind of basket, which contains a con¬ 
siderable quantity of dead leaves and other detritus drifted therein by wind, 
and mould formed by the decay of these and the older fronds. It is in this 
mass that the ants make their nest. 
On examining the material used by the ants for their nest in a fern 
put at some five or more feet from the ground in a tree, I found it consisted to 
a large extent of sand and minute fragments of laterite. These with frag¬ 
ments of decomposed vegetable matter formed the walls and covering of the 
nest. This material must have been carried up by the ants themselves. In 
moving a portion of the nest I found that the ants had a store of some 
species of coccid on the bark of the tree. This coccid was rounded in out¬ 
line and light brown in colour. It had doubtless been brought there by the 
ants, as I saw it nowhere else except in one portion of the nest where it was 
abundant. This coccid is orbicular, fawn-colour with the edges white, the 
whole surface dotted over with fine depressions or punctures. 
I believe the ant to be Dolichoderus taprobane . It appears to be 
identical with the species which makes its nest beneath the roots of 
Dendrobium crumenatum and other epiphytes. It is a very small species, 
little over 2 111m. long ; the head dark brownish above, abdomen nearly 
black, and the rest of the body and legs yellowish, all slightly hairy. It 
forms nests of soil, often in the form of a large sheet irregular and raised, 
under which an immense number live. Though very small they bite 
viciously, but the bite, though irritating, is not severe. They certainly attack 
other insects, and if a termite run in their neighbourhood is broken open so 
that the termite workers are exposed, the ants attack and carry them off. 
They will not, however, attack Termes umbrinus, a termite which is often 
to be seen going in long procession to or from a tree or woodwork, where it 
collects bark to cultivate a species of Agaricus , on which to feed the young. 
The army of T. umbrinus is guarded by soldiers flanking it, which repulse 
enemies by means of a corrosive liquid which they eject. The Dolichoderus 
may often be seen running by the army without attacking any of the 
termites. 
In the Platycerium it lives in vast myriads, and must bring up a 
considerable addition of clay and earth to the roots of the plant. The 
fronds of this fern do not spread so widely as do those of Thamnopteris , and 
are not nearly as efficient a trap for drifting leaves and sticks as are those 
of that plant, consequently the amount caught by the Platycerium is not 
