128 



Finally I may mention that I occasionally found well-con- 

 structed but abandoned birds' nests in the acacias. If these at 

 some former period really contained young birds, it is difficult 

 to see how these could have escaped being molested b\' the 

 Pseudomyrmas, 



The Ant Acacias of South America and Africa. 



Since Belt described the Central American acacias, species 

 with similar relations to ants have been discovered in South 

 America and Africa, and as these are not without interest in con- 

 nection with the foregoing observations, I may be pardoned for 

 briefly discussing them. 



South American ant acacias are known only from Paraguay. 

 In 1896 Emery enumerated the following series of ants as having 

 been found by Dr. J. Pohls nesting in the robust, wooden 

 thorns of a species of Acacia in that country : Pseudomyrma 

 acanthohia Emery, Leptothorax spininodis Mayr, Cryptocerns 

 pusillus Klug, pilosus Emery, hohlsi Emery, peltatus Emery, 

 quadratus Mayr, pallens Klug, grandinosus F. Smith, Cremato- 

 gaster hrevispinosa Mayr, and Myrmelachista nodi fera Mayr var. 

 flavicornis Emery. Most of these species seem merely to excavate 

 galleries in the woody tissue of the thorns, without hollowing 

 them out after the manner of the Central American ants. Ps. 

 acanthohia perforates the thorns near the tip, the other species 

 nearer the base. The latter often make several openings in the 

 same thorn. 



Much more like the conditions in the Central American acacias 

 are those recently described by Fiebrig (1909) for Acacia cavenia 

 H. and A. of Paraguay. The pairs of thorns on this tree are often 

 greatly enlarged and are frequently inhabited by an ant, Ps. 

 fiebrigi Forel, which makes its opening near the tip of one of the 

 thorns. Fiebrig found that the thorns are often hollowed out 

 by a Tineid larva, and he believes that the cavities thus formed 

 are later appropriated by the Pseudomyrma. No Beltian bodies 

 were found on the few plants on which they were sought, and 

 no mention is made of the extrafloral nectaries. The acacia 

 grows only in low grounds which are occasionally flooded, and 

 where there are no leaf-cutters. 



Even more interesting are the East African ant-acacias which 



