The Army Ants 



By T. C. SCHNEIRLA 

 American Museum of Natural History 



[With 2 plates] 



The Dorylines, one of the eight major subfamilies of ants, range 

 throughout the Tropics and sub-Tropics of the world. They have 

 survived very successfully from early Tertiary times, or at least 65 

 million years, on the basis of the unique combination of a nomadic 

 behavior pattern with a fully carnivorous way of life. All that we 

 now know about these ants and their relatives supports Wlieeler's 

 (1913) surmise that an exclusively carnivorous diet could not have 

 persisted together with a fixed nest miless colonies were to become 

 very small. In the ponerine and myrmecine subfamilies, which pre- 

 sumably are direct offshoots of the doryline ancestor, a largely car- 

 nivorous diet is widely characteristic as are fixed nests, but in species 

 following this pattern small colonies are the rule (Haskins, 1951). 

 But in doryline evolution the problem of large colonies and a car- 

 nivorous diet has been solved through a nomadic pattern of existence. 



The dorylines have an impressive reputation of long standing as 

 marauding insects, typified by Wlieeler's (1913) characterization of 

 them as "the Huns and Tartars of the insect world." General de- 

 scriptions of their interesting temporary nests or "bivouacs" were 

 available in the earlier literature, and from the observations of Savage 

 (1849) and Vosseler (1905) in particular on the African species of 

 Dorylus {Anomma) and of Sumichrast (1868), Belt (1874), Miiller 

 (1886), Bates (1863), and others on the New World ecitons, it seemed 

 that in all probability the nomadic way of life must characterize the 

 entire subfamily. 



Reading this literature in 1930, as a psychologist interested in prob- 

 lems of "instinct," I was at once struck by the impressive breadth 

 of the Eciton problem and by the fact that no real solution had been 

 found. On preliminary consideration, the prevalent hypothesis of 

 food exhaustion (Vosseler, 1905) seemed doubtful to me as an ex- 

 planation of nomadism in these ants, yet no good alternative presented 



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