136 



these, for some unknown reason, often becomes considerably 

 enlarged and bears a long, slit-shaped impression. It is in this 

 impression that the queen ant makes the circular perforation 

 that permits her to enter and take possession of the internodal 

 cavity. This recalls the conditions in Cecropia, and suggests 

 that ants may be able, through their extremely delicate tactile 

 (or rather chordotonal) sense-organs, to select for perforation 

 the thinnest spot in the wall of a cavity. The cavities in the 

 branches of T. macombii are occupied by several species of ants 

 belonging to the genera Crematogaster, Pheidole, Tapinoma, and 

 Iridomyrmex, but two species are especially common, a small 

 black, narrow-headed Azteca, and the black Pseudomyrma 

 sericea Mayr. Colonies of all of these species may be found 

 nesting in the internodes of the same branch, but the Pseudo- 

 myrma is the most abundant and aggressive. It stings quite as 

 severely as its congeners on the acacias, but, unlike the Ps. 

 arboris-sanctcB of Triplaris cumingiana, it does not take possession 

 of the whole tree, to the exclusion of other species. It is, more- 

 over, a common ant in the hollow twigs of many different trees. 

 As T. macombii is a large, vigorous tree, with coarse leaves that 

 can hardly tempt the leaf-cutters, I fail to see how it derives 

 any benefit from its motley assortment of ant-tenants. But that 

 the ants find the hollow internodes of the Triplaris the most 

 suitable of habitations can hardly be doubted. 



BIBLIOGRAPHY. 



1884-86. Beccari, O., Piante ospitatrici ossia piante formicarie dalla 



Malesia e della Papuasia — Malesia, ii., Genova, 1884-86. 

 1874. Belt, Thomas, The Naturalist in Nicaragua. London, 1874. 

 1842. Bentham, George, Notes on Mimoseae, with a Synopsis of species — 



Lond. Joum. Bot., i., 1842, pp. 503-4. 

 1900. BuscALONi & HuBER, J., Eine neue Theorie der Ameisenpflanzen — 



Botan. Zentralbl., 1900, Beihefte, pp. 85-8. 

 1697. CoMMELiN, J., Rariorum plantarum Horti Medici Amstelodamensis 



Descriptio et Icones. Amstelodami, 1697. Tom. i., p. 209, 



tab. 107. 

 1877. Darwin, Fr. On the Glandular Bodies of Acacia sphœrocephala 



and Cecropia peltata serving as food for ants, with an appendix 



