ARMY ANTS — SCHNEIRLA 387 



ing traffic, the major workers often stand around or blunder in the 

 paths of others. But although their fimction in traffic appears to be 

 mainly negative and indirect rather than specifically directive, it is 

 an important function, since collisions and traffic blocks incidentally 

 play a contributory role in the development of Eciton raids and the 

 emigrations which occur as their sequels. Although the major 

 workers never are seen carrying anything, the submajors normally 

 carry larger booty objects, and are particularly effective in carrying 

 the large male larvae when these are present in the colony. On the 

 whole, booty objects are carried, roughly, in relation to size by the 

 workers, with the smallest burdens carried by the minim workers. 

 Workers, major and submajor, as well as the largest intermediates, 

 play a particularly useful role in the construction and maintenance of 

 the bivouac. Because of their long legs and well-developed tarsal 

 hooks, these individuals become strong parts of the substructure in the 

 temporary nest, and normally can hold together under external dis- 

 turbances such as wind or rain. 



It is plain that polymorphic diiferences in the Eciton worker series 

 account for a corresponding relative specialization as in many other 

 ants. The intermediate Avorkers are prominent in activities outside 

 the bivouac and do the bulk of the effective raiding. Because of their 

 size, moderate proportions, and agility they are better suited for 

 ferreting out, attacking, and transporting booty, and laying down 

 chemical trails and traveling on them through varied and difficult 

 terrain, than are the largest and smallest castes. On the other hand, 

 the Eciton minors are an asset in transporting and feeding the brood, 

 particularly when it is in the Qgg and earliest larval stages. Wlien a 

 colony has a brood of eggs or very young larvae, these generally are 

 found in large boluses in the center of the bivouac, surrounded and 

 permeated by minim workers. So these diminutive workers, which 

 presumably received the least amount of food and w^ere most stunted 

 of all in their own larval brood, come into their own as mature workers 

 through being physically best suited for the early transport and feed- 

 ing of the young brood, a function of critical importance in colony life. 



ITie pillaging activities of the dorylines mark them as a unique 

 subfamily among ants — one with a constant predatory challenge to 

 the environment. Two principal types of raiding pattern are found, 

 exemplified by the column-raiding Eciton ]iamatu7n and the swarm- 

 raiding hurchelU^ and apparently expressed in degrees of difference 

 through the dorylines. The most arresting and dramatic raids are 

 those of the swarms that are formed daily by hurchelU colonies 

 (fig. 2). The hurchelU forays grow much larger than the somewhat 

 similar mass raids of praedator^ and cause far more commotion in 

 the forest. 



