The Maricopa harvester ant, Pogonomyrmex maricopa, is one of the most common species of harvester ant species found in Arizona, USA.^[1] Its venom is believed to be the most toxic insect venom in the world.^[2]

Their nest mounds are likely to incorporate rocks and gravel. The ants construct cemented caps on the sand mound nests in a fine sand dune area. The caps are approximately 60% calcium carbonate that is transported from the underlying calcium carbonate layers, and protect the nest structure from being eroded away during high-wind periods. Partial erosion of the cemented caps adds calcium carbonate to the sand dune soils.^[3]

Venom and attack method

The toxicity of the venom of the Maricopa harvester ant is well known. Its LD₅₀ value is 0.12 mg/kg (injected intravenously in mice); 12 stings can kill a 2-kg rat. In comparison, the LD₅₀ of the honey bee is 2.8 mg/kg — less than 1/20th as strong. In humans, a Pogonomyrmex sting produces intense pain that can last up to four hours.^[2][4]

Like many venomous insects, the venom of the Maricopa harvester ant consists of amino acids, peptides, and proteins. This may also encompass alkaloids, terpenes, polysaccharides, biogenic amines, and organic acids. The most notable component found in the venom of the Maricopa harvester ant is an alkaloid poison—this releases an "alarm" pheromone that chemically alerts other ants in the vicinity. This is an example of chemical signaling, which explains why ants all appear to sting at once. The venom can also contain allergenic proteins that are otherwise known to set off a potentially lethal immune response in certain victims.

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.

Sightings

Colonies of harvester ants have been reported in El Paso County, Texas. One sighting, recorded on August 14, 2004, reported a rather large Pogonomyrmex maricopa nest, measuring 6 by 24 ft (1.8 by 7.3 m), around which all surrounding vegetation had been cleared. The person who reported the sighting noted the length of the Maricopa harvester ant at approximately one centimeter.^[5]

Another sighting, recorded on July 26, 2001, in West Dog Canyon in Guadalupe Mountains National Park, Texas, described the ant-hill as consisting of excavated chambers that had a possible depth of 7 feet (2.1 m) or more.^[6]

These ants are also seen in New Mexico.^{[citation needed]}

References