I had great photos and lost them all to a computer bug that was even more vicious.
When the Velvet Mesquite is in bloom on the state land in Picture Rocks, Arizona, I spend a lot of time staring at the catkins. They are full of insect life, but most of it is both cryptic and tiny, including our smallest bees with the nice name Perdita, the lost one. To find one check the top of the catkin in the right half of the picture above.
|Pseudomyrmex sp. and Lycaenid caterpillars|
|Vanduzea laeta and Crematogaster Ants|
But caterpillars? Dave Wagner states in his book Caterpillars of Eastern North America: 'It turns out that nearly half the worlds 5500 lycaenid species (blues, coppers, hairstreaks) is tended by ants. In some species the association is so tight that the ants even carry the caterpillars to and from their nests' (where some species turn into brood parasites) and back to the feedings site on the proper host plants. The caterpillars of ant tended species have dorsal nectar glands on the 7th abdominal segment. From those, they periodically release a sugary substance. Most feed on flowers or fruit so they have access to excess sugar. The caterpillars can even call for the ants by vibration, but I got the impression that my ant was also trying to stimulate the caterpillar. If predators attack the caterpillar the ants will probably defend it, but I think in the most primitive form of this symbiosis the caterpillar is simply paying off the ants who otherwise might be the most dangerous predators themselves. The six legged mafia.
I saw the ant leave a couple of times and climb deeper into the tree. Pseudomyrmex are arboreal ants so the nest was probably inside a hole of a tree branch. Even though it was close to sunset and the wind was gusting, again and again there was an ant sitting on the caterpillars. I never saw more than one, perhaps always the same individual.
To me it was a surprise that an ant of the same genus as the tree-garding Bull-horn Ants of Costa Rica would be in a close relationship with caterpillars in Arizona.
To see a video of the ant with the caterpillars. Please click!
A nearby Catclaw Acacia was still in full bloom and females of Marine Blues were depositing their eggs. I assume that my caterpillars are of the same species.