A424 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
dozens, always finding the ant. The colonies contain an enormous 
number of individuals living throughout the whole plant, all parts of 
which are hollow. The workers are very aggressive and their sting 
is quite severe. Whether or not the ants derive any advantage from 
the tree other than a convenient place to nest I do not know, but 
there is no doubt that they protect the plant from almost any possible 
enemy. A Swiss rubber explorer, Otto Schmidt, who has spent many 
years in the forest and is a keen observer, told me that dead Triplaris 
plants never contain ant colonies. This suggests that the living 
plants do offer some attraction to the ant, other than shelter. 
64. Pseudomyrma oculata F. Smith. 
Many workers and females were found at Natal, nesting in hollow 
twigs. This is one of the smaller, more delicate species, the workers 
measuring 4 mm. in length. The'head is two and a half times as 
long as broad, the sides parallel with large, flat eyes. The antennal 
scapes are short, extending only to anterior third of eyes. The petiole 
is flattened above, twice as long as broad, in profile nearly twice as 
long as thick. The color is dark fuscous throughout. 
65. Pseudomyrma caroli Forel. 
Many colonies were found at Itacoatiara, nesting in twigs on small 
trees near the river. 
66. Pseudomyrma nigriceps F. Smith. 
Several workers were found at Abund and Madeira-Mamoré Camp 
41. 
This species resembles P. rufa in structure and size. The color is 
different and striking, the head being black, and the rest of the body 
and appendages testaceous. It was not common. 
67. Pseudomyrma flavidula F. Smith. 
Common at Independencia and Cearé-Mirim, nesting in grass culms, 
the characteristic nesting site of the species. 
