A review of micromorphological studies of ant and termite's epigean nests located in neotropical soils of Argentina

Abstract

This publication brings an integral revision about the micromorphology of ant and termite's nests located in neotropical soils. The building materials, wall microstructures, wall coatings, and building techniques are comparatively addressed, and illustrated with new photographic material. The soil nests were assigned to termites Termes saltans, Cortaritermes fulviceps, Cornitermes cumulans, and ants Atta vollenweideri, Camponotus punctulatus, Solenopsis sp, and Acromyrmex fracticornis. These species construct epigean structures, such as mounds and turrets in frequently flooded Mollisols, Ultisols, Alfisols and Entisols of the northern east region of Argentina. The building materials, i.e. soil components, plant fragments, and feces, were distributed and assembled in the nest walls forming characteristics micromorphological features, showing distinct differences with the adjacent soil micromorphology. Termites constructed very hard mounds with compact microstructures composed of soil pellets and grains closely assembled and cemented with feces, showing only thin fissures and very small vughs in their external walls. Interiorly, the walls of growing termite mounds displayed porous microstructures and a distinct parallel arrangement of organic laminae in the hive. Mounds and turrets of ants were constructed with humid soil pellets, firmly adhered without any kind of cement, forming spongy microstructures with mamillated and star-shaped vughs. This porous structure alternated with massive and crack structures, resulting from the breakdown of the wall aggregation by the percolated rain. Many species of ants and termites lined the mound and turret's galleries with feces or fine soil material. An active reorganization of the building materials over time was demonstrated in growing colonies of C. cumulans by means micromorphological analysis of young and mature nests. Likewise, removal of building materials and microstructures was also recorded in turrets of A. vollenweideri constructed in the laboratory with different building materials that were offered consecutively. In addition, the effect of rains on the removal of the pelletal aggregation was experimentally demonstrated. The building technique of turrets of A. fracticornis was revealed in field experiments, recording over time the intermeshing of plant fragments around the nest opening, and its simultaneous cementation with soil pellets.