Pheidole militicida
Pheidole militicida is a spectacular ant that occurs in southern Arizona. The minor caste is large (for a Pheidole), roughly the same size as those of Pheidole rhea. What is really neat about them, though, is that their major caste is very large, with a huge head. The head of the majors is so large that they seem awkward when they walk.

Dr. Wheeler first described the ant. When he went to visit the nests in the fall he didn't find any major workers in the nest, but he did find the remains of major workers in the midden pile. He hypothesized that the minor workers killed the major workers in the fall, perhaps so that the ants would not need to feed and maintain the major workers through the winter. Hence the name "militicida" - "soldier killer". Most people now believe that the major workers are just relatively shy, remaining deep within the nest much of the time. That is probably the explanation for the disappearing major workers.

I had never seen Pheidole militicida but was most eager to do so. Fortunately, my friend Lloyd Davis knew where to find them. We went out to the desert flats around Arizona's Whetstone Mountains. This surprised me - I had always assumed that they occurred at higher elevations. I had driven by Pheidole militicida dozens of times, not even slowing down! Argh!

The workers forage in streams. Their nest entrances were simple holes in the ground about the diameter of a pencil lead. There had been heavy rains recently, so if the ants had had nest mounds the rains would have washed them away. We put out some cookie baits and waited...and waited....no major workers appeared. I was starting to see why Dr. Wheeler came up with his "militicida" theory from. Eventually, though, a single major worker did come out. Wow! It was well worth the wait. It was like watching a Christmas tree ornament walk around. While the minor workers were a brownish-black, the major was a bright orangeish red. Its head was so large that I was surprised it was able to fit out of the small nest entrance.


  

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Pheidole militicida minor workers eating cookie bait
Pheidole militicida minor workers eating cookie bait
Side view of Pheidole militicida minor worker eating cookie bait
Side view of Pheidole militicida minor worker eating cookie bait
Pheidole militicida major and minor workers
Pheidole militicida major and minor workers
Pheidole militicida major worker, top and rear view
Pheidole militicida major worker, top and rear view
Pheidole militicida major worker
Pheidole militicida major worker
Pheidole militicida major worker
Pheidole militicida major worker
Pheidole militicida major and minor wokers.
Pheidole militicida major and minor wokers.
Pheidole militicida minor workers at a cookie bait. For scale, that is my finger in the lower left--hand corner of the photo.
Pheidole militicida minor workers at a cookie bait. For scale, that is my finger in the lower left--hand corner of the photo.
Pheidole militicida minor workers bring insect prey into their nest.
Pheidole militicida minor workers bring insect prey into their nest.