48 Zoologica: N. Y. Zoological Society [HI; 3 



at least the young colonies of nearly all of the twig-inhabiting 

 ants of British Guiana and the list of these is a long one, com- 

 prising many small species of Cryptocerus, Procryptocerus, Pseu- 

 domyrma, Leptothorax, Crematogaster, Azteca, Tapinoma, 

 Myrmelachista, Camponotiis, etc. 



4. Thief-ants. The only species belonging to this category 

 is the tiny Solenopsis altinodis Forel, (Fig. 15). which is closely 

 related to a series of "lestobiotic" Solenopsis species that nest in 

 the walls of ant-or termite-nests and prey on their brood. It 

 does not live in the Tachigalia petioles but enters those inhabited 

 by the social beetles, when their entrances happen to be un- 

 guarded, and destroys their larvae. In all probability it also 

 attacks small, defenceless colonies of the inquiline ants and 

 devours their brood. I infer that it nests in the ground from 

 the fact that it often appeared suddenly in considerable numbers 

 during the night and exterminated the colonies of the Pseudo- 

 myrmas in vigorous Tachigalia and Triplaris branches that had 

 been left on a table in the yard of the laboratory. I have also 

 seen it wandering about on the laboratory tables indoors, over 

 the foliage of the undergrowth in the dark jungle or feeding 

 on the pulp of injured fruits of the water cocoa (Pachira aqua- 

 tica Aubl.) growing along the river banks. 



5. Obligatory Ants. I would thus designate the ants that 

 are definitively attached to the Tachigalia as their host-tree. 

 There are only four species : Pseudomyrma damnosa sp. nov., 

 (Fig. 13), Ps. maligna sp. nov. (Fig. 14), with its two varieties, 

 cholerica and cnicians, Azteca foveiceps sp. nov. (Fig. 16), and 

 A. train Emery. The last is doubtfully included for reasons to 

 be given below. The recently fertilized queens of these ants 

 perforate and enter the petioles of young Tachigalias growing in 

 the shade, close the openings behind them with particles gnawed 

 from the walls and eventually produce their broods in the cavi- 

 ties. Occasionally queens of the two species of Pseudomyrma 

 or of these and A. foveiceps may be found, each in a petiole of 

 the same plant and even of one with only a few leaves. That 

 the founding of the colonies may be frought with many dangers 

 is shown by the fact that dead queens are often found shut up 

 in the petioles precisely as in the case of the Azteca queens in 

 the internodes of young Cecropias. Some of the unfortunate in- 



