Harvester Ant

California Harvester Ant (Pogonomyrmex californicus)

Order: Hymenoptera; Subfamily: Myrmicinae

Common throughout California, this ant is usually pale reddish color, but some workers in Southern California are black and reddish. Workers are about 1/4″ in length. This species has a large head with long hairs on its chin that aid in removing soil during excavation in the ground. The nest is generally a low flat crater in sandy soil. Workers seal the nest entrances at night and reopen them in the morning. These ants gather seeds, which are stored in the nests, the entrances to which are frequently surrounded by husks. If water gets into the seed areas, the ants will move the seeds to keep them dry, and after a rain they may carry the seeds to the surface to dry. Harvester ants can bite and sting. The sting can produce a red, painful inflammation which lasts several days. – John Carson

Powell and Hogue, California Insects
Hogue C.L., Insects of the Los Angeles Basin

During a study* of the impact of the Argentine ant in the Reserve in 1997-98, about 30 different species of ants were identified, and additional species are believed to be here. Unfortunately the invasive Argentine ant (Linepithema humile) is spreading its territory in the Reserve, displacing native ants including harvester ants, the preferred food of the coast horned lizard.

Next example: Oak Gall Wasp


* The Effects of an Invasive Ant by “Ant” Jamie King

ant-ArgentineIn the mid-1990’s, park visitors became familiar with my Master’s research by way of the little metal “cages,” brightly colored flags and buried jelly jars that dotted areas of the Reserve. Although at times an eyesore, these little contraptions served a vital role in furthering one of the primary goals of Torrey Pines State Reserve—to increase our understanding of the ecology of our local flora and fauna—specifically, to aid our understanding of the local ant populations.

Why ants? And who cares, really? As ants are the primary aerators of soils, distributors of native seeds, and a food source for native reptiles, we should all care. For this reason I studied the diversity, or variety, of native ant species across the reserve to determine whether this diversity is impacted when faced with the invasion of an exotic ant.

This invasive ant, the Argentine ant (Linepithema humile) is most commonly seen in our kitchens and bathrooms as a stream of erratically moving little black forms. They are also very common in coastal patches of native habitat in Southern California. In our Reserve they gang up on native ants, and with the ferocity of wolves subdue their opponents. The key to their success is ferocity and abundant numbers. Several will grab hold of the legs of native ants with their biting mandibles, others the antennae, and snap away until their opponent is dead. At times they will even drag these corpses, which are 5 – 10 times their size, back to their nests. The final fate of the dead is unknown.

What we do know, however, is that over the long haul, the Argentine ant is displacing our native ant species. My research has shown that ant diversity is significantly decreased when the Argentine ant is present. In other words, there are fewer native ants and native ant species. And this effective invader is spreading across the Reserve at what appears to be a rate of approximately 100 meters per year. Only the Parry Grove, the southern portion of the Guy Fleming, and areas closer to the beach are presently free of this ant. If measures are not taken to limit further expansion of the Argentine ant, we can expect these areas to be infiltrated as well.