1921] Wheeler: Some Social Beetles 49 



sects undoubtedly succumb to hunger or the attacks of fungi, 

 but in many cases they seem to be killed by alien ants or by the 

 beetles boring into the same petioles. If the queens survive, 

 however, and produce their broods of workers, the latter open 

 from the inside the entrances made by the queens and eventually 

 take possession of the whole plant. Since all the petioles of 

 larger trees are invariably inhabited by a single flourishing 

 colony of a single species or variety, we must suppose that the 

 offspring of different queens on opening their respective petioles 

 either fight for the possession of the plant or, if they belong 

 to the same species or variety, unite to form a single polycladic 

 colony. The fact that the petioles of large trees contain several 

 dealated fertile females of Ps. damnosa or maligna would seem 

 to indicate that the eventual climax colony, as it may be called, 

 is established by alliance of several broods rather than by the 

 survival of the offspring of a single queen. Furthermore, the 

 climax colony seems to be far too populous to represent the off- 

 spring of a single mother. 



No sooner are the petioles opened by the young broods of 

 workers than the coccids enter or are carried in by the ants and 

 attach themselves to the areas of nutritive parenchyma which 

 furnish optimum conditions for feeding and growth. Here they 

 can multiply and be cared for by the ants which undoubtedly 

 find in them a most welcome source of food. As the tree grows 

 and puts forth new leaves, each young petiole as soon as it has 

 reached the proper size is perforated by a detachment of ants and 

 coccids. The later leaves, as I have stated, have cavities extend- 

 ing nearly the entire length of the petioles and adjacent to their 

 insertions there are also cavities in the branches, which are like- 

 wise entered and occupied by the insects. The largest leaves have 

 petioles with such broad cavities at their bases that the ants 

 find it necessary to make chambers in them by building carton 

 partitions. The materials for the carton are gnawed from the 

 walls. Azteca foveiceps builds a much more elaborate system of 

 partitions than the Pseudomyrmas. This is not surprising, be- 

 cause the Aztecas are nearly all wonderful experts in carton 

 construction. 



When the climax stage of the Tachigalia biocoenose has been 

 reached, it has been reduced to only three organisms, the plant, 



