Observations on mating flights of Pogonomyrmex tenuispina
    by Ken Manson
photos by Gordon Snelling

      Pogonomyrmex tenuispina has fascinated me every since I first saw their huge workers walking up a steep foraging trail in the foothills above La Quinta, near Palm Desert California several years ago. I had wanted to find a mating lek and witness colony founding in substrate that most, if not all, Pogo species would never inhabit. (ed note. Pogonomyrmex anzensis nests in a similar habitat) The ground is very inclined and consists of cracked, gravely soil with many rocks and obstacles. This is the only Pogonomyrmex species I have found in this particular area.
      So this last September 2, when I heard about thunderstorms in the area the day before, I decided to make the long drive from Southern Orange County out to the steep incline in the hot desert this species calls home. Unfortunately, these storms were not predicted and I had left my digital camera at work. I verified this area had, in fact, received measurable precipitation and decided to make the drive early the next morning.
     On a few stops out there this summer, when the morning temperatures reached 90 degrees F by 9:00AM, there were no signs of foraging activity by the time I arrived. But this morning, I arrived earlier at 7:45AM and the ambient temperature was about 80 degrees F. The sun's full light had not completely covered the hill and the ground was soaked from the night before. I reached the first colony in a few minutes-and my heart started racing! Not only were there countless alates of both sexes on the surface, but they were being examined and groomed by older callows and adult sisters. I checked a few more colonies and sure enough, they all had alates and worker attendants. About 8:00AM, as the sun rose further into the sky, the males began to take off. Some of them did try to grab a hold of and mate with their sister females, but the females always moved away. None of the female sexuals left with the males. Not one. They all stay around the nest opening moving around our getting groomed. I watched the males take off and circle the nest area 2-4 times before heading up wind and therefore up the steep canyon.
      I tried to keep track of where they were heading to, so I could find them in a little while. But they flew so high, it was simply impossible. Around 8:20AM, the females started to fly, first circling the nest and heading in the same direction as the males. Some of them needed to climb grass stems or other nearby plants, to gain some advantage during takeoff. By 8:45AM, all the females had left their nests and all that was left were foraging workers. I hiked for over an hour looking for possible leks--on Ocotillo plants, rock outcroppings, flat areas with little vegetation--you name it. But, I could not find one mating site. I thought they all must have gone too far up the canyon to find any, but I did find a few dealates while walking back to my car around 10:30AM. By then, the heat and physical exertion had taken its toll and I had to call it a day. I wish I had some pictures to share, but I hope you find this shared experience of some interest. I hope to return next summer, fully prepared with my digital camera and all the proper tools of scientific documentation to properly record a similar event.

Habitat shot 1
Habitat shot 2
Colony entrance
Cover stone lifted