NEW FORMICID^E FROM BARRO COLORADO ISLAND. 155 



particles. During the summer of 1920 I examined some of the 

 colonies of S. urichi, which were nesting in the lawn near Mr. 

 Urich's laboratory in Port of Spain, but time to make a careful 

 investigation was lacking. During the same summer I took in 

 the sandy area adjoining the Tropical Laboratory of the New 

 York Zoological Society at Kartabo, British Guiana, a few 

 workers of a Sericomyrmex which I have recently described as 

 impexus (1924), but I failed to reach the chambers in the very few 

 nests that were excavated. 



My sojourn on Barro Colorado Island finally yielded the 

 desired opportunity to study not only Sericomyrmex but also 

 several other Attini. During the height of the rainy season this 

 locality is a veritable myrmecological and mycological paradise. 

 Within a few hundred yards of the laboratory (Fig. i) numerous 

 colonies of at least 14 species of fungus-growing ants could be 

 found, all with their gardens close to the surface of the ground and 

 easily accessible. I recognized two species of A tta, one of 

 Acromyrmex, three of Trachymyrmex, three of A ptero stigma, three 

 of Cyphomyrmex, one of Myrmecocrypta and one of Sericomyrmex. 

 Thus nearly all the known genera of Attini were represented. 

 Further search will probably reveal the presence of Mycocepurus 

 on the island. Nor were the ants the only fungus-cultivating 

 insects. The trunks of the trees that had been felled during the 

 dry season (spring of 1924), when the small clearing was made 

 around the laboratory, had reached a stage when they attracted 

 thousands of ambrosia beetles of the family Platypodidae. During 

 June and July these insects were everywhere making their long 

 tubular fungus-lined galleries in the dead wood and covering the 

 logs with their frass. It would, indeed, be difficult to find a more 

 favorable locality for mycological investigations, not only on 

 account of the interesting fungi cultivated by so many ants and 

 beetles but also of the extraordinary number and variety of other 

 fungi, which during the rainy season flourish in all parts of the 

 jungle. 



Leaving an account of the other Attini for consideration at 

 some future time, I will here confine my remarks to the Seri- 

 comyrmex which harbors the Megalomyrmex in its gardens. This 



Sericomyrmex seems to represent an undescribed species, which I 

 11 



