Messor pergandei, continued

Messor pergandei's nests are a common and conspicuous element of the desert around Phoenix. They are characterized by one or more entrances surrounded by varying amounts of chaff. The chaff piles can range from nonexistent in the case of young nests or fresh nest entrances to luxuriant piles several centimeters deep. Often it will appear that there are several nests in close proximity to each other, as in the photos to the right. Evidently these are multiple entrances to a single nest. The ants will often have several active entrances, each with a chaff mound, for each nest. The entrances typically seem to be within 15 or 20 feet of each other. In a phenomenon that is similar to Lincecum's "ant rice", you can see that the mounds in the photos at the right are surrounded by relatively lush vegetation, especially after the winter rains. The effect is especially striking in relatively barren areas such as the desert pavement in these photos.
The photo at the far right is another picture of a Messor pergandei nest after the winter rains. This one is surrounded by gold poppies. The photo on the near right was taken during (one of the) dry seasons. The white object in the photo is a six inch ruler. Note the lushness and depth of the midden, forming a mound around the nest. "Young" nest entrances' midden piles usually start in a relatively restricted arc around the entrance, forming a crescent which expands in depth and arc proscribed until the entrance is eventually surrounded. Wind and rain storms clear out the middens periodically. The photographs on the lower right are closeups of the chaff pile around a Messor pergandei nest entrance. The small furry objects that are visible in the chaff pile are the coat from creosote seeds (Larrea). Most of the long, curved objects are the seed pods of gold poppy. As I recall, one of the entrances to the nest in the photo to the far right is under/around the rock in the upper left quadrant of the photograph.
Messor pergandei tends to forage in long columns. During active periods, there may be more than one column of ants streaming to and from the various nest entrances. While Messor pergandei seems to be more likely to be out and about on days of moderate temperature, I haven't had much luck predicting the activity on days of more extreme conditions. Activity tends to be in the mornings and evenings (and nights?) during the hottest time of the year. Messor pergandei is also sometimes active on days that I assumed would be too cold - 55-60 degrees fahrenheit.

The picture on the far right shows a nest entrance during an active period. Note the lack of a large chaff pile, in spite of the number of ants and size of the nest entrance. The photo on the near right shows some Messor pergandei bringing seeds back into a nest entrance. The different size classes of ant is evident here.


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