3'4 



ANTS. 



iliis plant, when growing in the Antilles, fails to develop the hollow 

 >wellings in the stems. The hollow twigs of the Polygonaeeous Tri- 

 plitris. or " palo sanlo," of which some twenty species are known, are 

 said to he invariably occupied hy Pseudomyrma. Of these ants Forel 

 ( i<)04/) says: " Through the investigations of Mr. Ule the fact becomes 

 more and more firmly established that a definite group of Pscudoin\nua 

 species ( arboris-sanc tec, dcndroica and triplaridis) lives symhiotically 

 in the natural medullary cavities of Triplaris. In 1896 I myself 



FIG. 181. Mound of Formica e.vscctoidcs .70 meters high and 2.46 meters in 

 diameter, almost completely covered with a moss (Polytrickum commune) which 

 eventually envelops the summit of thr nest and extinguishes the colony. (Original.) 



observed in Colombia how /'. arboris-sanctce var. symbiotica fiercely 

 attacked anyone who touched the tree. Their brood filled the whole 

 living tree from the trunk to the smallest green branches. They seemed 

 to have entered this secure and ramifying domicile through a small 

 dead and broken branch on the lower part of the trunk." 



Xo doubt the various cases cited in the preceding pages are of great 

 interest, both to the botanist and myrmecologist, but it is equally certain 

 that none of them has been studied with sufficient care to warrant the 

 conclusions advocated by Belt, Schimper and others. The relation- 

 ships under discussion are all compatible with the view that the ants 

 have adapted themselves to the plants plantas itaquc norunt formica" 

 but the converse of this proposition is in most, if not in all instances, 

 open to doubt. Travelers and naturalists who observe for a short 



