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Texas Invasive Species Institute

Texas Invasive Species Institute

Black Crazy Ant

Paratrechina longicornis

Class: Insecta
Order: Hymenoptera
Family: Formicidae

Paratrechina longicornis

Photographer:Unknown Affiliation:Pest and Diseases Image Library Source:www.bugwood.org Copyright:CC BY 3.0


Adult Description: The black crazy ants, are called that because of their random, erratic and quick movements. For Paratrechina longicornis the worker ants are small (2.3-3 mm) and are dark brown to blackish on the head, thorax, petiole and gaster. However, the body has a faint bluish iridescence and has long, coarse and sub-erect grayish or whitish hairs (setae). The antennae have 12 segments without a terminal club, and they appear extremely long. The legs are extraordinarily long. Also, there is no stinger but a crazy ant may bite when threatened and then inject a formic acid secretion into the wound.

Ecological Threat

Workers are omnivorous and can feed on live or dead insects, seeds, fruit, household food or honeydew excreted by aphids. They have been known to gather small seeds from crops such as lettuce or tobacco from seedbeds; preventing the establishment of the plant for the new growing season. One thing that makes them an ecological threat is their feeding behavior; they forage long distances away from their nests which makes them hard to control. Also, because they are closely associated with disturbed human habitats they are easily dispersed by human activity, and being a very hardy species they are hard to eradicate. Paratrechina longicornis has been observed to displace native ants and other invertebrates, which always has as strong ecological impact, especially with ant because of how ecologically important and diverse ants are. Finally, in Brazil Paratrechina longicornis has even been known to bring multiple pathogenic microbes in hospitals. Luckily, this has not been observed in the United States but it definitely not something to overlook.


Overall there is not much know about their life history; but what is known is even though these ants are found in close proximity to human dwellings, they always nest outdoors. Colonies are polygyne (multiple queens) and usually contain around 2,000 workers and 40 queens and they can live in habitats that are very dry or relatively moist. In Florida, alates (sexually mature individuals) are raised in the warm and rainy months; while in other areas of the country, alates can be produced any time of the year.


This ant was first observed in Florida in 1930, by 1950 it was found in warehouses all over the eastern United States. In 1984 it was found as far west as California and Arizona. Since then it has been found in New York, Massachusetts, Hawaii, Missouri, Virginia and all Gulf Coast states.

Native Origin

possibly Southeast Asia

Current Location

The black crazy ant can occur within homes or outdoors; so it can be found anywhere from houses and apartment buildings to hotels to kitchens or even inside cars parked near houses. Since it can persist indoors there is no limit to the latitude where it can exist.



Being a crazy ant Paratrechina longicornis has the same erratic behavior as the Tawny Crazy ant (Nylanderia fulva) when they’re startled. Also, they tend to nest in the same habitats and are both are invasive.

For more information on the Tawny Crazy ant click here.


A clean house and protected food sources can help prevent these ants from entering the house. Also, with caulking and weather-stripping at exterior entrance points. Indoor chemical baits can be used along with the pesticide Termidor (i.e.: Fipronil). That same pesticide can also be used as an outdoor treatment and should be sprayed around the perimeter of the house.   


Fowler, H. G.; Bueno, O. C.; Sadastsune, T.; Montelli, A. 1993. Ants as potential vectors of pathogens in hospitals in the state of São Paulo, Brazil. Insect Science and its Applications, 14(3):367-370.

Smith MR. 1965. House-infesting ants of the eastern United States; their recognition, biology, and economic importance. USDA Technical Bulletin 1326. 105 pp.

Garcia, F. R. M., & Lise, F. 2012. Ants associated with pathogenic microorganisms in brazilian hospitals: attention to a silent vector-doi: 10.4025/actascihealthsci. v35i1. 10471. Acta Scientiarum. Health Science, 35(1):9-14.

Moreira, D., Morais, V. D., Vieira-da-Motta, O., Campos-Farinha, A. E. D. C., & Tonhasca Jr, A. 2005. Ants as carriers of antibiotic-resistant bacteria in hospitals. Neotropical Entomology, 34(6):999-1006.

Wetterer, J. K., Miller, S. E., Wheeler, D. E., Olson, C. A., Polhemus, D. A., Pitts, M., ... & Burgess, T. L. 1999. Ecological dominance by Paratrechina longicornis (Hymenoptera: Formicidae), an invasive tramp ant, in Biosphere 2. Florida Entomologist, 381-388.

Wetterer JK. 2008. Worldwide spread of the longhorn crazy ant, Paratrechina longicornis (Hymenoptera: Formicidae). Myrmecological News 11:137-149.

Internet Sources





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