Ants of the genus Acropyga Roger, with description of a new species.

Within recent years Acropyga, which seemed to be a rather insignificant genus of tropical Formicine ants, has been acquiring a reputation as a serious though indirect pest in certain South American countries. The receipt of an undescribed species of this genus together with its very interesting symbiotic coccids from Mr. E. J. H. Berwick of the Imperial College of Tropical Agriculture in Trinidad, B. W. I., has led me therefore to review briefly some of the published accounts of these insects. Emery, in the "Genera Insectorum" (1925), has divided the genus Acropyga into four subgenera: Acropyga s. str. (5 species), Rhizomyrma Forel (18 species), Atopodon Forel (5 species) and Malacomyrma Emery, with a single species. Acropyga and Atopodon are confined to the Indomalayan and Papuo-Australian regions. Rhizomyrma has a similar distribution in the Old World but is also represented and by an even greater number of species in Middle and South America and in the Antilles. The single species of Malacomyrma (M. silvestrii Emery) is known only from Eritrea. At first sight the workers of all four sub genera closely resemble those of our North American species of Lasius of the subgenus Acanthomyops Mayr in their small size, smooth, yellow integument and small or vestigial eyes, but closer examination shows that they are peculiar in having a reduced and variable number of antennal joints in all three castes. More over, like the species of Acanthomyops, all the Acropygae are ex quisitely hypogaeic, or subterranean ants devoted to fostering and disseminating root-coccids. Since the ants and their cher ished coccids may be locally very numerous, especially in planta tions, it is easy to see how certain economic plants may suffer serious injury through loss of sap or more indirectly, as will be shown in the sequel, by infection with pathogenic organisms transmitted by the coccids, after they have been transported to healthy plants by their hosts. The following accounts, with one exception, refer to species of Rhizomyrma and their coccids.