8 Intense Facts About Crazy Ants

Anoplolepis gracilipes, yellow crazy ants, on moss plant
frank600 / Getty Images

Crazy ants are about 1/8 inch long and are on the march to invade ecosystems worldwide. There are at least 21 species of crazy ants inhabiting North America today.Two notable ones are yellow crazy ants and tawny crazy ants.

Crazy ants get their name from the way they travel. They move about randomly, creating zigzags rather than the straight lines of other types of ants. Take some time to learn about these wildly successful insects that have an outsize impact on their environment.

1. Crazy Ants Are an Invasive Species

Typically, when the IUCN talks about a species, it is threatened or endangered. Yellow crazy ants break that pattern as they are listed as one of the world's worst invasive species by the group. Tawny crazy ants — also called Rasberry crazy ants — showed up in Houston, Texas, in 2002, before spreading. Longhorn crazy ants, endemic to tropical Africa, now have spread to every continent except Antarctica.

Crazy ants seem like they'd be unlikely invasive species as they don't fly or walk long distances. Instead, these ants rely on humans to move them long distances. Plants, mulch, firewood, cars, and other mobile "homes" are all potential sources of crazy ant infestations in new locations.

2. They Are Winning the Turf War With Fire Ants

Crazy ants can save themselves from fire ant venom by grooming themselves with an antidote they secrete from a special gland. Instead of a stinger, they have a fire ant anti-venom gland. The substance is formic acid, and its use is two-fold: the same antidote that they use to nullify venom on themselves is used as a chemical weapon against competitors, including the fire ants.

3. They Congregate in Huge Numbers

Crazy ants form supercolonies that stretch for miles. One spotted on Christmas Island covered more than 1,800 acres.

Without natural competitors keeping them in check, in the U.S., they can "attain densities up to 100 times as great as all other ants in the area combined," according to Ed LeBrun of The University of Texas at Austin. That density creates nightmares for people in their path. Crazy ants will swarm over pets, people, animals, and plants. It's not unusual for gallons of them to be removed from air conditioners and swept from sidewalks after extermination.

4. They Are Known for Shorting Out Electronics

Crazy ants and their foraging lead them to electrifying places, literally. They frequently infest air conditioning units, traffic signals, electronics, appliances, and outlets. When they enter these areas and get shocked by a hot wire, they release a pheromone calling the colony for help. This results in nearby ants coming to the scene. They, in turn, get shocked, calling more ants. Millions of ants flood the area filling the AC unit or television, eventually shorting out the appliance and leaving piles of dead ants inside. This has even been a problem for places like the Johnson Space Center in Houston.

5. Their Nests Contain Many Queens

Instead of a single queen tended by workers, a crazy ant supercolony contains dozens of queens. This supports their large colony size and frequent moves to new areas to forage. In ant species with multiple queens, the worker ants don't attack foraging ants from other colonies of the same species. That lack of aggression allows the genetic diversity needed to increase colony size successfully.

6. They Cause Significant Harm to Other Species

The yellow crazy ant is responsible for significant losses of Christmas Island's iconic red land crabs and reducing the island biodiversity. They spray formic acid on the crab's joints, paralyzing and killing them. That species also has caused seabird injuries and deaths in Hawaii and the Johnston Atoll. Crazy ants damage honeybee populations through their swarming attacks on beehives. They have even caused chicken deaths through asphyxiation after the ants crawl into the birds' nasal passages.

7. Scientists Are Seeking Biological Controls

Because the supercolonies of crazy ants stretch over long distances and have so many individual ants, traditional ant control methods don't work. Mechanical means such as closing off access to food by blocking access can only go so far. Crazy ants aren't attracted to most traditional bait pesticides, either. Their lack of natural predators in the areas where they are invasive adds to the difficulty in managing populations. To combat these issues, researchers are looking at using integrated pest management to control the ants. They hope to use parasitic flies, wasps, or fungi to attack the ants in conjunction with pesticides and mechanical methods.

8. Some Species Farm Their Own Food

Yellow crazy ant protect aphids on a cherry
Poravute / Getty Images

In addition to their damaging effects on animals, crazy ants also form mutualistic relationships with some insect species. The ants protect various honeydew-producing insects from predators and milk them with their antennae. Honeydew is a sweet secretion from the insects that the ants eat. These insects include aphids, whiteflies, mealybugs, and other bugs that eat plants. The resulting increase in scale insects causes the dehydration and death of plants in their path.

Help Prevent the Spread of Crazy Ants

  • If you visit a location with crazy ants, inspect your belongings and vehicle for signs of ants before leaving.
  • Check potted plants, bagged mulch, and soil for ants before adding to your landscape.
  • Purchase local firewood when camping. Don't bring it home with you.
  • Seek professional help for infestations. Readily available consumer products are ineffective and harm desirable plant and animal species.
View Article Sources
  1. "North American Ants." Myrmecos.

  2. "Crazy Ants." The University of Texas at Austin Brackenridge Field Laboratory.

  3. "100 of the World's Worst Invasive Alien Species." Global Invasive Species Database.

  4. Ferro, M.. “Common Name Selection in the Internet Age: A Crazy Case Study.” American Entomologist, 2013, pp.136-137.

  5. Chen, Jian, et al. "Defensive Chemicals of Tawny Crazy Ants, Nylanderia Fulva (Hymenoptera: Formicidae) and their Toxicity to Red Imported Fire Ants, Solenopsis Invicta (Hymenoptera: Formicidae)." Toxicon, vol. 76, 2013, pp. 160-166, doi:10.1016/j.toxicon.2013.09.018

  6. "Christmas Island Yellow Crazy Ant Control Program." Australian Government.

  7. "Invasive crazy ants are displacing fire ants in areas throughout southeastern US." EurekAlert, 2013.

  8. "If you build it, they will come." Roundup, 2017.

  9. LeBrun, Edward G., et al. "Ritualized Aggressive Behavior Reveals Distinct Social Structures in Native and Introduced Range Tawny Crazy Ants." PLOS ONE, vol. 14, no. 11, 2019, p. e0225597, doi:10.1371/journal.pone.0225597

  10. "Loss of biodiversity and ecosystem integrity following invasion by the Yellow Crazy Ant (Anoplolepis gracilipes) on Christmas Island, Indian Ocean." Australian Government.

  11. Farmer, Chris. "Invasive Ants In Hawai'i: Small Species, Big Problems." American Bird Conservancy, 2017.

  12. "TAWNY CRAZY ANT, RASBERRY CRAZY ANT." Texas Invasive Species Institute.

  13. Wang, Zinan et al. "A Review of the Tawny Crazy Ant, Nylanderia Fulva, An Emergent Ant Invader in the Southern United States: is Biological Control a Feasible Management Option?Insects, vol. 7, no. 4, 2016, p. 77, doi:10.3390/insects7040077

  14. O'Dowd, Dennis J., et al. "Invasional 'Meltdown' on an Oceanic Island." Ecology Letters, vol. 6, no. 9, 2003, pp. 812-817, doi:10.1046/j.1461-0248.2003.00512.x