'Pogonomyrmex maricopa', the Maricopa harvester ant, is one of the most common species of harvester ant found in the U.S. state of Arizona, but it is also known from California, Colorado, New Mexico, Nevada, Texas and Utah, and the Mexican states of Baja California, Chihuahua, Sinaloa and Sonora. Its venom is believed to be the most toxic insect venom in the world.

The toxicity of the venom of the Maricopa harvester ant is well known. In comparison the honey bee is less than 1/20th as strong. In humans, a 'Pogonomyrmex' sting produces intense pain that can last up to four hours. Similar to the two-part process of the fire ant bite and sting, the harvester ant will attach to the victim with its mandibles, and so proceed by pivoting around the site, allowing the ant to repeatedly sting and inject venom into the region.

The Maricopa harvester ant plays a major role in decomposition by dragging dead carcasses of insects underground, thereby enriching soil for plants and crops.

More Info: en.wikipedia.org