Yapp . — Two Malayan ‘ Myrmecophilous ’ Terns. 215 
hairs or scales, which later dry up and leave a large empty 
space, which may or may not communicate with the exterior 
through the foliar gaps.’ 
A plant which may perhaps afford in some respects an 
interesting parallel to the case of the Ferns under considera- 
tion is Polypodium bifrons , Hook. The following note is 
appended to Hooker’s description of this Fern 1 : — 
‘ Hab. Ecuador, on a tree by the river side . . . the plants 
were partially immersed in water, and to the root or caudex 
were attached hollow succulent tubers, in which the ants had 
taken refuge.’ 
Unfortunately nothing appears to be known respecting the 
origin of the hollows referred to. 
The association of ants and Ferns is by no means limited 
to the cases already mentioned. Beccari 2 and Goebel 3 quote 
a number of instances in which the relationship varies from 
cases where the ants actually inhabit cavities in the sub- 
stance of the plant itself, down to those where the insects 
merely nest in the humus which collects around the roots and 
leaf-bases of so many epiphytes, both Ferns and flowering 
plants. In fact, one of the things which first strikes an 
observer in the tropics is the fact that ants are almost every- 
where present. Any convenient hole or corner, whether above 
or below the ground, generally affords shelter to a colony 
of ants. It is not surprising therefore that such eminently 
suitable nests as are afforded by the ramifying galleries of 
these Ferns, and the similar ones of Myrmecodia and Hydno- 
phytum , should be so invariably appropriated by ants 4 . The 
very ubiquity of the ants, however, combined with their 
undoubtedly high degree of intelligence, would suggest that 
they, like bees and other insects, may not have been without 
their influence on the evolution of plants 5 . Undoubtedly 
the mere presence of ants does sometimes protect plants from 
their insect enemies. Ludwig 6 cites several instances in which 
1 Hooker (’64), p. 79. 2 Beccari ( , 84- , 86), pp. 243 et seq. 
3 Goebel (’88), pp. 16 et seq. * 4 Cf. Treub (’88), p. 207. 
5 Cf. Lubbock (’91), p. 57. ® Ludwig (’95), p. 243. 
