Nests: Building, Structure, and Maintenance

Home, home building, and home improvement. Pogonomyrmex ants and their nests , at various locations in North America.
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Pogonomyrmex occidentalis

● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps » ● 6/24/10 6:32AM mostly sunny, air temp: 12°C / 53°F

The elongated mound of this large P.ogonomyrmex occidentalis nest was about 60cm / 2 ft wide, on its longest axis. The nest was oriented so that the side you see in this image faced east, receiving direct sunlight in the morning. The large cave-like main entrance can be seen in the center of the image (there was another smaller entrance just out of view on the northeast end). This mound sat in a 2.4m / 8 ft wide clearing, and was completely covered with gravel. The shrub just behind the nest is saltbush (Atriplex sp.). [scroll down for additional notes/references]

ADDITIONAL NOTES/REFERENCES: Many Pogo nests sport a prominent gravel-covered mound, cone, or crater which contains a small network of galleries and tunnels. In some cases, this mound feature is not present, and the external nest structure consists simply of entrance holes in the ground, often surrounded by a gravel 'disc', and located within an area cleared of vegetation. However, like the proverbial 'tip of the iceberg', the above-ground portion of a Pogo nest represents only a tiny fraction of the whole colony - in terms of ant population, and in the physical structure and extent of the nest itself. The subterranean portions of Pogonomyrmex nests usually contain one or more large (approximately vertical) tunnels - and branching off from these, many 'side burrows' and chambers. These offshoots are more numerous (and larger) nearer the surface, and dwindle in frequency and size, as depth increases. These chambers function as granaries, nurseries, general quarters, and sometimes refuse dumps. Pogonomyrmex nests can reach considerable depths. Nests of P. rugosus (the rough harvester) have been shown to extend 4 m / 13 ft into the ground, and those of P.occidentalis have been recorded to reach depths of 3 m / 10 ft. Along with distinct variations among different Pogo species, there are many variables that affect the proportions of a particular colony's nest. It's likely that most nests are somewhat shallower than the figures given above.

·MacKay, W.P. 1981. A Comparison of Nest Phenologies of Three Species of Pogonomyrmex Harvester Ants (Hymenoptera: Formicidae). Psyche, Vol. 88, No. 1-2, 1981 ·Taber, S.W. 1998. The World of the Harvester Ants. College Station, TX, Texas A&M University Press. ·Wheeler, W.M. 1910. Ants: Their Structure, Development and Behavior. New York, Columbia University Press