308 .4 NTS. 



by the American Museum of Natural History prove conclusively that 

 such an interpretation is erroneous. The wall of the hollow trunk, 

 where it encloses the nest, shows no structural modification except a 

 bending outward of the woody fibers. About half the thickness of 

 this wall is gnawed away by the ants from the inside, leaving a thin 

 zone encircling the trunk, which naturally bulges out under the weight 

 of the superposed trunk and crown of foliage. As there is no hyper- 

 trophy of the tissues in the spindle-shaped deformation, the term gall, 

 as applied to a structure of such simple mechanical origin, is a mis- 

 nomer. When the metropolitan nest is established the ants make a 

 large entrance in the adjacent wall of the trunk and through this and 

 the other openings in the branches pass to and from the foliage. They 

 collect the Aliillerian bodies and store them in the nest where they can 

 be eaten at leisure. So dependent is the Azteca colony on the Cccropia 

 for this food that it perishes when the tree dies or is cut down. 



Those who have seen the living imbauba and its occupants are 

 unanimous in describing the insects as rushing out and fiercely attack- 

 ing any one who ventures to touch the foliage. Alien ants, especially, 

 are vigorously assailed and either killed or driven from the tree. Von 

 Ihering, however, calls attention to the fact that various Chrysomelid 

 larvse, caterpillars and the sloth (Bradypns tridactylus) are permitted 

 to feed on the leaves unmolested. Fritz Miiller and Schimper believed 

 that the Aztcca protects the tree from defoliation by the large leaf- 

 cutting ants of the genus Atta, but von Ihering has shown that the 

 plant, even when entirely free from its so-called protectors, is rarely or 

 never visited by Atta. It thus appears that the Cccropia is not known 

 to have any enemies against which the Azteca could avail. The ani- 

 mosity of these ants is probably greatest against alien colonies of their 

 own species, and is directed to retaining possession of the feeding 

 grounds and neighborhood of their nest. This is, of course, a well- 

 known trait of ant-colonies in general. Although von Ihering says 

 that " in order to thrive the imbauba no more requires the Azteca than 

 a dog does fleas," he nevertheless believes that the Mullerian bodies and 

 the prostome are myrmecophilous adaptations. In this, he seems to 

 me, to concede too much, for if the ants are of no use to the Cccropia, 

 why should the latter develop structures for the purpose of attracting 

 and retaining this superfluous bodyguard? And of the three Cecro- 

 pian structures, which might be regarded as indicating myrmecophily, 

 namely, the cavities of the trunk and branches, the prostomes and the 

 Mullerian bodies, the first can hardly be an adaptation to harboring- 

 ants, the second are produced, or at any rate, started, as Schimper 

 admits, by the pressure of the axillary buds against the surface of the 



