RELATIONS OF ANTS TO VASCULAR PLANTS. 



295 



and thus converted into habitable tenements. In both cases the cavity 

 is entered through a small orifice which either preexists or is made by 

 the ants. This orifice then constitutes the nest opening, or entrance. 

 These simple requirements are fulfilled by a great many plant structures 

 which therefore make admirable domiciles for small ants that live per- 

 manently in small colonies or for incipient colonies of larger ants that 

 later form populous communities. The rigid vegetable tissues are an 

 excellent protection against enemies, and the cavities are moist, dark and 

 free from moulds, so that they make perfect nurseries for the larvae 

 and pupae. Cavities of this description are especially utilized by ants 

 in the tropics, probably because there these insects are more abundant 

 and the struggle for existence is keener. The following paragraphs 

 will show how numerous and variable are the plant organs that may 

 be tenanted by ants : 



1. Cavities in Stems. Almost any hollow or pithy stem, with 

 resistant walls sufficiently thin 



to be pierced by ants, may be 

 entered and occupied by these 

 insects. Some plants, how- 

 ever, are especially well-suited 

 to these purposes, for example, 

 those of the Old World genera 

 Randia, Myristica, Clcroden- 

 dron, Kibara and Bambusa, 

 with preformed cavities, and 

 Endospermum and Juglans 

 with pithy stems ; among the 

 New World genera : Cecropia, 

 Triplaris, Tacliigalea, Hum- 

 boldtia, Tachia, Ficus, Cordia, 

 Dnroia, Conssapoa, Ptcro- 

 cladon, Pterocarpon, Boin- 

 ba.v, Cladiuin, etc., with 

 preformed cavities, and Coc- 

 coloba nvifcra, S a p i u in , 

 Sclncartzia, Platymyschium 

 and Sauibncns with pithy stems. The entrances to the cavities are 

 actually foreshadowed as pits in the internodes in Cecropia and 

 Clcrodendron. 



2. Tubers, Bulbs, Pseudobulbs, Rootstocks, etc. Many examples 

 could be cited under this head. The most celebrated are the Malayan 

 Rubiaceous epiphytes of the genera Myrmccodia and Hydnophytnm, 



FIG. 1 66. Sterns of " mynr.ecophilous " 

 plants. (Escherich, after Schimper.) A, 

 Ficus inccqualis ; B, Triplaris americanus : 

 C, same, older stem ; D, Hnmboldtia 

 luiirifolia : .r, entrance to cavity of stem. 



