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Invasive Crazy Ants Are Displacing Fire Ants, Researchers Find

[caption id="attachment_40354" align="alignleft" width="300" caption="Image courtesy of Joe MacGown, Mississippi Entomological Museum"]Nylanderia_fulva_queenhead-web[/caption]


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The “ecologically dominant” crazy ants are reducing diversity and abundance across a range of ant and arthropod species but their spread can be limited if people are careful not to transport them inadvertently, according to Ed LeBrun, a research associate with the Texas invasive species research program at the Brackenridge Field Laboratory in the College of Natural Sciences






The crazy ants were first discovered in the U.S. in 2002 by a pest control operator in a suburb of Houston, and have since established populations in 21 counties in Texas, 20 counties in Florida, and a few sites in southern Mississippi and southern Louisiana.


The Tawny crazy ant invasion is the most recent in a series of ant invasions from South America brought on by human movement. The Argentine ant invaded through the port of New Orleans in about 1891. In 1918 the black imported fire ant showed up in Mobile, Ala. Then in the 1930s, the red imported fire ant arrived in the U.S. and began displacing the black fire ant and the Argentine ants.




LeBrun said that in northern Argentina and southern Brazil, where the ants are native, populations are likely held in check by other ant species and a variety of natural enemies. In the U.S. there is no such natural control.

Here the crazy ants can attain densities up to 100 times as great as all other ants in the area combined. In the process, they monopolize food sources and starve out other species. LeBrun said the crazy ants, which are omnivorous, may also directly attack and kill other ant and arthropod species.



LeBrun said a great deal about the Tawny crazy ants remains unknown, including their potential range. So far, most of the colonies are in fairly wet environments with mild winters, near the coast, so it may be the case that they can’t thrive in drier or colder climates, and that fire ants will remain dominant in those areas.

The spread of the Tawny crazy ants may also be limited, even within the more hospitable climates, by caution from humans. The reproductive members of the species don’t fly. So when left to their own devices, crazy ant colonies can only advance about 200 meters a year. That means they’re dependent on humans to colonize new areas.

“They are opportunistic nesters,” said LeBrun. “They can take up residence in everything from a house plant, to an empty container left outside, to an RV. So they’re easily transported by us. But the flip side of that is that if people living in or visiting invaded areas are careful and check for the crazy ants when moving or going on longer trips, they could have a huge impact on the spread.”  Nursery products also appear to be a key way these ants spread, so both buyers and sellers should be watchful for these ants.

