I4O WILLIAM MORTON WHEELER. 



dulcius. Among the few remaining species of true Eciton of 

 which the queen has persistently eluded capture is E. hamatum. 

 During the past summer (1924) I was fortunate enough to secure 

 a beautiful specimen of this insect from a bivouacking colony just 

 behind the new tropical laboratory on Barro Colorado Island in 

 the Panama Canal Zone. This find is, perhaps, the more 

 important because hamatum is the type of the genus and because 

 it has such a wide distribution (from Brazil to Mexico) and is so 

 common that its raids have been noticed by nearly every zoolog- 

 ical explorer in tropical America. It is, in fact, among the more 

 than one hundred described species of Eciton, the one which has 

 been longest known and most often cited in the literature since 

 Fabricius first described the soldier in 1781. 



At 8.00 A.M. on August 1st, after a heavy rain on the preceding 

 day, while collecting behind the laboratory I encountered an 

 army of Eciton hamatum foraging along the central trail (Fig. i) 

 and in the adjacent jungle. The workers were plundering 

 numerous nests of ants (Pheidole, Acromyrmex and Camponotus 

 species) and carrying away their helpless larvae and pupae. On 

 one of the tall trees they had found a large nest of a yellowish 

 wasp (Polybia sp.) and for some hours were bringing in the brood 

 in great quantities. Dr. Curt Richter devoted the morning to 

 watching the files, computing their rate of movement and the 

 nature of their prey. By following the various converging 

 columns we eventually located the colony which was bivouacking 

 less than a hundred yards from the laboratory near the edge of the 

 jungle. The great mass of ants presented an astonishing 

 spectacle (Fig. 2). They had selected the base of a small tree, 

 which, about 15 inches above the ground, was joined to the trunk 

 of a young stilt palm by a looped liana and some twigs, together 

 forming a horizontal frame. The larger tree trunk was inclined 

 to the north so that the surface of the bark and the ground 

 beneath were quite dry. In this spot, which had evidently been 

 sheltered from the heavy rains for several days, the ants had 

 congregated in a compact, cuboidal mass, 13 to 15 inches high and 

 broad, and suspended from the frame above mentioned. Dozens 

 of large workers hung by their claws from the twigs and supported 

 solid clusters and curtain-like sheets of workers and soldiers, the 



