Print this pageTraces and Burrowing Behaviors of the Western Harvester Ant Pogonomyrmex Occidentalis: Paleopedogenic and Paleoecological Significance
New observations are described on the burrowing behaviors, nest construction, and sediment mixing patterns of the western harvester ant Pogonmyrmex occidentalis (Insecta: Hymenoptera: Formicidae) based on neoichnological laboratory experiments. A glass-sided enclosure 38 cm (tall) x 38 cm (height) x 2 cm (wide) was filled with silty clay sediment to emulate a hypothetical A, C, Ab (buried horizon), Cb (buried horizon) aridisol profile (A/C/Ab/Cb). The A horizons were unaltered sediment collected from a terrace soil in Lawrence, Kansas; C horizons were produced by 4-hour loss-on-ignition at 500 degrees C of the unaltered material to remove all organic carbon. The top two layers of the experiment were ~9 cm thick; the bottom two layers were ~6 cm thick. Fifty ants were added to the enclosure, which was covered with tape to keep the ants from escaping, and allowed to burrow for 6 weeks. The galleries and chambers were mapped every 12 hours on 1 cm x 1 cm gridded transparencies for changes in nest ontogeny (development) and architecture. At these times the enclosure was photographed and ant behaviors were described and videotaped. The nest after 6 weeks was cast with dental plaster and used to study the architectural and surficial morphology of the nest. The result of the experiment was an intricate nest comprised of numerous interconnected galleries and chambers. Several excavating behaviors observed include raking, pushing, forcing, pulling, and carrying, which resulted in the excavation, construction, and modification of galleries and chambers. Chambers and galleries reached the bottom of the enclosure. Galleries varied in size but averaged ~1.5 cm in diameter. Chambers varied in size from a few cms long and wide to ~10 cm long and 2 cm wide. Ants that hung upside down pulled material from the ceiling to enlarge the chambers; other ants then removed this material as it became available. Excavated sediment was removed from all horizons and deposited at the surface, resulting in a large cone. Sediments were translocated upward as well as downward from horizons within the nest. This material was used to reinforce walls or to backfill previously constructed galleries and chambers. Colored sand introduced into the enclosure on the ant-modified surface was brought into the nest and carried down into the Ab horizon (~20 cm below the surface). Mixing occurred within and between all horizons as well from the surface; this plays a major role in soil formation.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009