Maricopa Harvester Ant

Pogonomyrmex maricopa

Maricopa Harvester Ant (Pogonomyrmex maricopa): One of the Most Toxic Insect Venoms

The Maricopa Harvester Ant (Pogonomyrmex maricopa) is a rusty-red seed-gathering ant of the US Southwest and northern Mexico with one of the most toxic insect venoms ever measured.

Schmidt pain rating

3 out of 4; pain can last 4 to 8 hours

Venom

LD50 0.12 mg/kg in mice, over 20× as lethal as honey bee venom

Look

Light to deep rusty red worker with a shiny abdomen

Range

SW United States to Sonora, Sinaloa, Chihuahua and Baja California

Diet

Seeds, plus dead insects and droppings

Conservation

Not evaluated by the IUCN

Habitat & range

The Maricopa Harvester Ant lives in western Texas, New Mexico, southern Colorado, southern Utah, Arizona, southeastern Nevada and southeastern California, and in Mexico in Sonora, Sinaloa, northern Chihuahua and northern Baja California. It occurs in all communities of the Chihuahuan Desert, especially on sandy soils, and is one of the few ants that can nest in loose sand, such as at White Sands in New Mexico. Maricopa Harvester Ant appears as an Insecta creature card in Wilder TCG.

Seeds and nests

Like other harvester ants, it gathers seeds. Workers forage on their own rather than in columns, collecting seeds, droppings and dead insects. Workers are light to very deep rusty red, with a moderately to strongly shining abdomen. Nests are usually in open sandy ground. East of El Paso, Texas, some nests were immense, with clearings up to 7 metres across and mounds approaching 2 metres high, though most of these have since been lost to urban growth. In a fine sand dune area, colonies built cemented caps on their mounds that were about 60% calcium carbonate, carried up from the layers beneath. The caps keep the nest from blowing away in strong winds, and as they erode they add calcium carbonate back to the dune soil. Winged queens and males fly from June to August.

One of the most toxic insect venoms

Justin O. Schmidt's venom tests made the Maricopa harvester ant famous: its LD50 (the dose that kills half of test animals) is 0.12 mg/kg injected into the veins of mice, so about 12 stings could kill a 2 kg rat. For years this was cited as the most toxic insect venom known, including in the University of Florida Book of Insect Records. That is more than 20 times as lethal as honey bee venom, whose LD50 is 2.8 mg/kg. In Schmidt's 2019 table of venom lethalities for 90 stinging insects, one species scored lower still: the Argentine harvester ant (*Pogonomyrmex cunicularius*) at 0.088 mg/kg. North American harvester ants ranged from 0.12 to 0.7 mg/kg. Harvester ant venom is mostly made of peptides that act on sodium channels in mammal nerves. A person would need hundreds to thousands of stings for the venom to be life-threatening, but the stings hurt for hours. These ants are known as extremely pugnacious defenders of their nests.

The sting

Schmidt rated the sting of *Pogonomyrmex maricopa* a 3 on his 4-point pain scale and described it as: "After eight unrelenting hours of drilling into that ingrown toenail, you find the drill wedged into the toe." (Schmidt, *The Sting of the Wild*, Johns Hopkins University Press, 2016). In people, a harvester ant sting causes intense pain that can last from four to eight hours. Schmidt first came up with his pain scale after being stung by a harvester ant.

Conservation

*Pogonomyrmex maricopa* has not been evaluated for the IUCN Red List. It is widespread across the desert Southwest, although some of its largest known nests, near El Paso, have been destroyed by urbanization.

Fun facts about Maricopa Harvester Ant

• Its venom has an LD50 of 0.12 mg/kg in mice, so about 12 stings can kill a 2 kg rat. For decades it was cited as the most toxic insect venom known.
• By that measure it is more than 20 times as lethal as honey bee venom (LD50 2.8 mg/kg).
• In sand dunes the colonies build cemented caps on their mounds that are about 60% calcium carbonate, carried up from the layers below.
• Near El Paso, Texas, some nests had cleared areas up to 7 metres across and mounds approaching 2 metres high.
• It is one of the few ants able to nest in loose sand, such as at White Sands in New Mexico.
• In Schmidt's 2019 table of venom lethalities for 90 stinging insects, only the Argentine harvester ant (0.088 mg/kg) was more lethal.

Maricopa Harvester Ant vs Tarantula Hawk Wasp

One on one, the tarantula hawk wins this card battle; against a whole defending colony it would be a different story.

There is no record of these two fighting; this is a Wilder comparison of two of the desert Southwest's most famous stingers. Schmidt rated the harvester ant's sting 3 and the tarantula hawk's 4, and in that region only the tarantula hawk outranks harvester ants for pain. A single small ant is no match for a large flying wasp, but the ant's venom is among the most lethal ever measured in insects, and a colony defends its nest together.

Read more about Tarantula Hawk Wasp.

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