These images depict Pogonomyrmex occidentails
workers in the state of Nevada, USA. This is the well known 'western harvester ant'.
Scroll down PAST BOTTOM OF PAGE for complete image description, and CLICK large image to make it even LARGER...
Scroll down PAST BOTTOM OF PAGE for complete image description, and CLICK large image to make it even LARGER...
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 6:13AM mostly sunny, air temp: 12°C / 53°F
[IMAGE 1 of 2] I arrived at this large Pogonomyrmex occidentalis colony, just as the sun was coming up from behind the hills. This was one of only two workers visible outside of the nest at this early hour.](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-cjxwPMm/0/Ti/4477_10_7Df-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 6:13AM mostly sunny, air temp: 12°C / 53°F
[IMAGE 1 of 2] I arrived at this large Pogonomyrmex occidentalis colony, just as the sun was coming up from behind the hills. This was one of only two workers visible outside of the nest at this early hour.")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 6:14AM mostly sunny, air temp: 12°C / 53°F
[IMAGE 2 of 2] I arrived at this large Pogonomyrmex occidentalis colony, just as the sun was coming up from behind the hills. This was one of only two workers visible outside of the nest at this early hour.](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-jz85Wfv/0/Ti/4484_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 6:14AM mostly sunny, air temp: 12°C / 53°F
[IMAGE 2 of 2] I arrived at this large Pogonomyrmex occidentalis colony, just as the sun was coming up from behind the hills. This was one of only two workers visible outside of the nest at this early hour.")
![pogolumina > ● 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.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](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-6PMc8Gr/0/Ti/4223_10_Rc-Ti.jpg "pogolumina > ● 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.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")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:01AM mostly sunny, air temp: 14°C / 58°F
Two Pogonomyrmex occidentails workers emerging from the nest. It is not uncommon to see a considerable size variation among workers from the same colony, as can be seen in this image.](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-SvCjpTm/0/Ti/4550_10_7Df-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:01AM mostly sunny, air temp: 14°C / 58°F
Two Pogonomyrmex occidentails workers emerging from the nest. It is not uncommon to see a considerable size variation among workers from the same colony, as can be seen in this image.")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:18AM mostly sunny, air temp: 16°C / 61°F
[IMAGE 1 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-j4wXRkK/0/Ti/4564_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:18AM mostly sunny, air temp: 16°C / 61°F
[IMAGE 1 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:36AM mostly sunny, air temp: 18°C / 64°F
[IMAGE 2 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-WjmqZQx/1/Ti/4612_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:36AM mostly sunny, air temp: 18°C / 64°F
[IMAGE 2 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:47AM mostly sunny, air temp: 20°C / 69°F
[IMAGE 3 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-8GW2f6d/0/Ti/4637_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:47AM mostly sunny, air temp: 20°C / 69°F
[IMAGE 3 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:01AM mostly sunny, air temp: 20°C / 69°F
[IMAGE 4 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. The psammophore of this worker can be clearly seen. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-hhKKsxK/1/Ti/4645_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:01AM mostly sunny, air temp: 20°C / 69°F
[IMAGE 4 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. The psammophore of this worker can be clearly seen. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-rGMQncc/0/Ti/4680_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:35AM mostly sunny, air temp: 18°C / 64°F
[IMAGE 1 of 2] Some of the foraging P.occidentalis workers could be seen digging around in the sandy soil - it is unclear what they were searching for.](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-3ZJX2kV/0/Ti/4610_10_7Dc-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 7:35AM mostly sunny, air temp: 18°C / 64°F
[IMAGE 1 of 2] Some of the foraging P.occidentalis workers could be seen digging around in the sandy soil - it is unclear what they were searching for.")
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:12AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 2 of 2] Some of the foraging P.occidentalis workers could be seen digging around in the sandy soil - it is unclear what they were searching for. Many (like this particularly dark colored individual) were covered with soil particles as a result of their digging activities.](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-GJPVxVM/2/Ti/4668_10_7Df-Ti.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:12AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 2 of 2] Some of the foraging P.occidentalis workers could be seen digging around in the sandy soil - it is unclear what they were searching for. Many (like this particularly dark colored individual) were covered with soil particles as a result of their digging activities.")
![pogolumina > ● 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](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-DzHqNVw/0/Ti/2224_10_40Dc-Ti.jpg "pogolumina > ● 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")
● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982
![pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982](http://www.pogolumina.net/NorthAmericanPogosbySpecies/Pogonomyrmex-occidentalis/i-rGMQncc/0/M/4680_10_7Dc-M.jpg "pogolumina > ● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982")
● SW of Pyramid Lake [Washoe Co], NV USA [el. 1323 m / 4341 ft] view location in Google Maps »
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
● 6/24/10 8:20AM mostly sunny, air temp: 22°C / 72°F
[IMAGE 5 of 5] About two dozen P.occidentalis workers started foraging along an approximately 4.5m / 15 ft long trunk trail [1], that extended from the nest in a northwesterly direction. Some of them began finding petals from saltbush plants (Atriplex sp.), and carrying them back to the nest from as far away as 3m / 10 feet. [scroll down for additional notes/references]
ADDITIONAL NOTES/REFERENCES:
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982
Pogonomyrmex occidentalis, and P.salinus are generally regarded to be 'trunk-trail foragers'. In many cases, multiple, well established trails lead away from the nest in different directions. Workers travel along these paths to the end, and then disperse, or 'fan out' to search individually for seeds or other food items. After securing something (or in many cases failing to do so), the ants return individually to the nest by way of the trunk trail. In many Pogonomyrmex species, trunk-trails have been shown to be oriented so that foraging ants from neighboring colonies avoid mass confrontations during their searches for food. This allows there to be a greater density of nests in a given area, with minimal conflict.
These trails are initially established (and reinforced) by pheromones laid down by the ants. In at least one species (P. barbatus), foraging workers are influenced in their choice of which of multiple trails to utilize on a given day, by 'patrollers' - workers who leave the nest first in the morning, and scout the area. They then lay a short chemical trail with secretions from the Dufour's gland, from the nest entrance to the start of a particular trunk-trail(s). Evidence suggests that the direction chosen by the patrollers is not so much based on food availability, but by their encounters with patrollers from neighboring colonies.
The visibility and length of trunk-trails can vary greatly. The P.salinus trails we have observed so far (in Oregon and Washington states), while occasionally very visible (and free of vegetation), are more often indistinct, and not easily observable unless ants are traveling along them. As mentioned elsewhere on this site, we have observed trunk-trails of Pogonomyrmex salinus 9m / 29.5ft or more in length - though it is our experience that they are usually much shorter - and many nests (the majority in some locations) have no visible trails.
We also observe these ants foraging individually near the nest, in Oregon and Washington states.
·Greene, M.J. & D.M. Gordon. 2007. How Patrollers Set Foraging Direction in Harvester Ants. The American Naturalist, Vol. 170, No. 6, December 2007
·Hölldobler, B.1974. Home Range Orientation and Territoriality in Harvesting Ants. Proceedings of the National Academy of Sciences USA, Vol. 71, No. 8, pp. 3274-3277, August 1974
·Hölldobler, B. & E.O. Wilson.1990. The Ants. Cambridge, MA, Belknap/Harvard Press
·Johnson, R.A. 2000. Seed Harvesting Ants (Hymenoptera: Formicidae) of North America: An Overview of Ecology and Biogeography. Sociobiology Vol.36, No. 1, 2000
·Jorgensen C.D. & Porter, S.D. 1982. Foraging Behavior of Pogonomyrmex Owyheei in Southeast Idaho. Environmental Entomology, Vol. 11, No. 2, April 1982