|Mounds of the Leaf-cutter Ant, Acromyrmex versicolor, left and right. Middle: Smooth Harvester Ant Messor pergandei|
I must admit that I lived surrounded by those ants for years before it dawned on me that there were two very different species at work and the differences are quite apparent.
At one type of colonies, the single minded efforts of a never ending procession of ants result in an accumulation of fresh green, purple or silver plant clippings that sit there for a day and then disappear into the crater (top right). These are the leaf-cutter ants that I will describe in a later blog.
The plant material circling the other type of colonies looks old and discarded. The ring around the mound seems to be the permanent waste midden of the colony (above, middle).
This is the work of the Smooth Harvester Ant Messor pergandei. In this and the following blog I will not describe the social structure of ant communities that both species have in common, but rather point out the most striking differences in the way of life in these two local crater-building species...
|Messor pergandei, the Smooth Harvester Ant|
|Erodium cicutarium, Redstem Filaree|
Messor ants like Erodium diaspores so much that most middens that I checked in March 2012 consisted of nothing else. This raises the question whether seed dispersal is actually achieved. While the seeds are removed from the mother plant, they still end up in dense piles, exposed to elements and rodents. If this is a glitch in the system, it's probably because Erodium and Messa really didn't co-evolve. I would like to observe the behavior of local ants in the Mediterranean home countries of the plant. But, alas, when I studied insects in Yugoslavia, Greece, and Italy, ants were not very high on my list. However, if the spread of Erodium in our backyard and the adjoining state land is any indication, it's a successful symbiosis, even here in Arizona.
|Veromessor pergandei refuse heap in October after a good monsoon: hulls of cheat grass seeds are rejected and piled around the nest entrance|
|Messor pergandaei queen|
Pogonomyrmex, and that was the most painful insect encounter I can remember (and I have been attacked by fireants in Florida)
|Pogonomyrmex sp. nest and worker|
P.s. the Genus name Messor has been changed to Veromessor for the US species since I wrote this entry