'Crazy' Ants Driving Out Fire Ants in Southeast

Nylanderia fulva, also known as the tawny
crazy ant, hails from northern Argentina and
southern Brazil. CREDIT: Joe MacGown,
Mississippi Entomological Museum

'Crazy' Ants Driving Out Fire Ants in Southeast
May 17, 2013 | Live Science | Douglas Main

Invasive fire ants have been a thorn in the sides of Southerners for years. But another invasive species, the so-called "crazy" ant — that many describe as being worse — has arrived and is displacing fire ants in several places.

"When you talk to folks who live in the invaded areas, they tell you they want their fire ants back," said Edward LeBrun, a researcher at the University of Texas at Austin, in a statement from the school. "Fire ants are in many ways very polite. They live in your yard. They form mounds and stay there, and they only interact with you if you step on their mound."

Crazy ants, on the other hand, "go everywhere," invading homes and nesting in walls and crawlspaces, even damaging electrical equipment by swarming inside appliances. [Image Gallery: Ants of the World]

A study published in the April issue of the journal Biological Invasions found that in areas infested with crazy ants, few to no fire ants were present. Exactly how they are able to outcompete fire ants is so far unknown. In areas with crazy ants, the researchers also found greatly diminished numbers of native ant species, according to the study.

Fire ants are known for their painful stings and have spread through the Southeast since arriving from South America in the 1930s. Crazy ants were first discovered in Houston in 2002, and they have already spread to coastal areas from Texas to Florida, according to the researchers. Although the "crazies" don't have as painful a sting as fire ants, they multiply in even greater numbers. They are also difficult to control since they don't eat the same poison baits as fire ants do, the statement noted.

Last year, the crazy ant species was identified as Nylanderia fulva, which hails from northern Argentina and southern Brazil, according to a 2012 study in PLOS ONE. It's also known as the tawny crazy ant and was previously named the Rasberry crazy ant after the exterminator Tom Rasberry, who first discovered it. The "crazy" moniker comes from the ant's quick, seemingly random movements.

Luckily, the crazy ant doesn't spread as quickly as the fire ant, advancing only 650 feet (200 meters) per year on its own, the release noted. Therefore, it's vital that people don't accidentally transport the ant, the prime method by which it has spread, according to the release.

Email Douglas Main or follow him on Twitter or Google+. Follow us @livescience,  Facebook or  Google+. Article originally on LiveScience.com.

Fire Ant Monarchy Ruled by 'Social Chromosome'

A 616-gene sequence ("social chromosome")
determines whether a single queen or many
will rule a colony of fire ants, Solenopsis invictaI.
Here, a queen, three smaller workers and one pupa.
CREDIT: Romain Libbrecht and Yannick Wurm

Fire Ant Monarchy Ruled by 'Social Chromosome'
Jan 16, 2013 | Live Science | Stephanie Pappas

Whether fire ants bow to one queen or accept many rulers depends on one long strand of genes, a new study finds.

The gene sequence is the first "social chromosome" ever discovered, according to study researcher Yannick Wurm of Queen Mary, University of London, who called the DNA sequence a "supergene."

"This was a very surprising discovery," Wurm said in a statement. "Similar differences in chromosomal structure are linked to wing patterns in butterflies and to cancer in humans, but this is the first supergene ever identified that determines social behavior."

Choosing queens

The fire ant Selenopsis invicta is one of many fire ant species known for nasty stings. The species is native to South America and invasive elsewhere. One of its odder traits is a particular flexibility about its social structure. Some members of the species live in colonies with a single queen, while others tolerate hundreds of queens. [Gallery: Stunning Photos of the World's Ants]

The new genetic analysis, published Thursday (Jan. 17) in the journal Nature, finds that a sequence of genes on a certain chromosome determines which social arrangement is acceptable to the ants. Much in the same way that the human sex chromosomes vary between X and Y, the ant chromosomes vary between B and b.

If all the workers in a colony carry the B variant only, they will accept a single queen that also carries only the B variant (marked as BB, because the chromosomes come in pairs). But if some workers in the colony carry the b version of the chromosome, the colony will accept multiple queens — but only those queens with a mismatched "Bb" set of chromosomes.

Worker fire ants with only the B variant
of the social chromosome will accept a single
queen also with only the B variant
(described as "BB"). But if the queen has the
other variant, the so-called Bb queen, she will
be attacked by these BB workers (shown here).
CREDIT: Chih-Chi Volans Lee,
Yu-Ching Huang and John Wang

Smelly queens?

The chromosomal differences have been linked to a number of anatomical differences in the ants, Wurm and his colleagues wrote, from the queen's fecundity to the size of male workers and the structure of their sperm. These differences could explain how the ants "know" what sort of monarchy to accept.

"Odor is likely involved," Wurm told LiveScience. "We know the queens smell different."

The two different genes may also confer their own advantages. BB queens mate and disperse to their own colonies when they reach maturity, making them good at invading new areas, the researchers wrote. Bb queens join others near their maternal colony and, working together, produce more workers overall. This might make them more successful in previously colonized areas.

Wurm and his colleagues plan to dig deeper into the chromosome to find out which of the 616 genes in the social sequence are responsible for the differences between ants. They also hope to find out if similar sequences play social roles in other species. And the differences aren't just academic. The fire ants have spread into the southern United States as well as Australia and China, where they are major pests.

"Our discovery could help in developing novel pest-control strategies," Wurm said. "For example, a pesticide could artificially deactivate the genes in the social chromosome and induce social anarchy within the colony."