● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps » ● 6/24/10 8:28AM mostly sunny, air temp: 22°C / 72°F Another P.occidentalis nest, about 12 m / 40 ft from the previous one pictured. This cone-topped mound was approx. 30 cm/ 1 ft in height, and perfectly covered with gravel. Workers can be seen at the extreme right corner of the image, where the single entrance was located. [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