During a quick hike through South Mountain Park in Phoenix, Arizona yesterday, I spotted a Messor Pogonomyrmex rugosus harvester ant mound.
The refuse or midden pile was covered with a fluffy material.
The ants apparently have been collecting the seeds of this plant, and discarding the seed coats.
It is a common plant in the Sonoran desert. Do you know what it is?
The plant is a food source to a range of insects as well as Messor harvester ants, including more than 20 species of bees.
It is the common creosote bush, Larrea tridentata.
The midden piles of harvester ants, as with many other types of ants, are known to improve the nutrient levels in the soil in the immediate area.
Tomorrow I will post more about Messor harvester ants.
Hum, now that I think about it, I wonder if "midden piles" is redundant, because midden is a trash heap. Anyone out there help me out on this?
Edit: Thanks to Alex Wild for pointing out that these ants were Pogonomyrmex rugosus, not Messor.
Edit: Here's a photo of Pogonomyrmex rugosus.
For more information, try:
Dale Ward has some videos of Messor pergandei in action, as well as more information
More about cresote bush and the Zygophyllaceae (caltrop family) at the Arizona-Sonora Desert Museum