Harold G. Fowler

HOST-SPECIFICITY OF SEVERAL PSEUDACTEON (DIPTERA, PHORIDAE) PARASITES OF FIRE ANTS (HYMENOPTERA, FORMICIDAE) IN SOUTH-AMERICA

We tested the host specificity of several parasitic Pseudacteon scuttle flies in South America with 23 species of ants in 13 genera. None of these ant species attracted Pseudacteon parasites except Solenopsis saevissima (F. Smith) and to a lesser extent Solenopsis geminata (Fab.). This result is encouraging because it indicates that the Pseudacteon flies tested in this study would not pose an ecological danger to other ant genera if these flies were introduced into the United States as classical biological control agents of imported fire ants. This prediction of host specificity will, of course, need to be validated with potential hosts in the United States before these flies can be released.

Distribution patterns of Paraguayan leaf‐cutting ants (Atta and Acromyrmex) (Formicidae: Attini)

Abstract 432 transects were run in 19 sites in Paraguay, encompassing 8 major habitat types, to examine the distribution patterns of the taxa of leaf‐cutting ants. Colonies of Acromyrmex were significantly correlated with decreasing habitat complexity, while colonies of Atta showed a similar, though non‐significant, trend. A mean of 3.04 species of leaf‐cutters was found per site, with a maximum of 7 species recorded. By comparing colony incidences of one genera with the other, intra‐generic competition is suggested. Discriminant analysis indicated that pasture species and colony densities were much more like those of cultivated land, and that disturbed habitats were much more variable in species composition and colony densities than undisturbed habitats. Canonical correlation analysis of standardized colony densities of 15 taxa of leaf‐cutters and 6 gross habitat variables permited the identification and quantification of their interrelations, and explained up to 73% of the variation in colony densities....

Populations, prey capture and sharing, and foraging of the Paraguayan Ponerine Odontomachus chelifer Latreille.

Summary In central Paraguay, the ponerine ant Odontomachus chelifer is found in densities of less than one colony/ha in mixed woodland, and is almost always associated with Atta sexdens, the dominant leaf-cutting ant. Individual colony populations number less than 150. Foraging was found to be highly seasonal, and to be preceded by the formation of preforage aggregations. With increasing colony hunger, foraging activity increased. Moreover, definite preferences were shown for certain common termite prey species. With increasing colony hunger, less food was shared among workers.

Notes on Labidus praedator (Fr. Smith) in Paraguay (Hymenoptera: Formicidae: Dorylinae: Ecitonini)

Summary Labidus praedator was found throughout Paraguay in both forest and grassland habitats. Bivouac sites are described, and long-term bivouacs are confirmed. Estimates of brood production and colony size are given. Raids are described, and the environmental effects on the raiding pattern is analysed, both long-term and short-term.