Giant ants spread in warm climes

During the Eocene, continents were in different locations from those they occupy today

Here's an interesting story that BBC covered in the last few days about these wonderful animals and their migration that I found fascinating.  I have always found the ant to be a curious insect.  So, I will be covering this small invertebrate quite a lot in my blog.  Without further adieu, here comes another story on the ANT (Titanomyrma lubei).

A giant ant growing over 5cm (2in) long crossed the Arctic during hot periods in the Earth's history, scientists say, using land bridges between continents.

The ant, named Titanomyrma lubei, lived about 50 million years ago and is one of the largest ant species ever found.

Fossils were unearthed in ancient lake sediments in Wyoming, US.

Hummingbird and ant fossil showing size

Writing in the Royal Society Journal Proceedings B, a Canadian-US team shows that giant ants, now and then, almost always live in hot climates. The new species appears very similar to fossils found in Germany and in the Isle of Wight in southern England dating from the same period.

We don't have any [fossils of] workers from this new species, we only have a queen," said Bruce Archibald from Simon Fraser University in British Columbia. "It would have been very impressive - the one in Germany was estimated to have a body weighing as much as a wren, and this would have been of similar size," he told BBC News. Little is known about how these ants lived or what they ate - but wings are present on the fossils. They are found, in Europe and now in Wyoming, close to plants known to thrive only in temperatures around 20C (70F).

Road much travelled
The Eocene, 56-34 million years ago, was punctuated by periods when the Earth's temperature rose higher than it is today, probably because of the release of greenhouse gases such as methane into the atmosphere.
And the researchers believe that the giant ants must have made a journey from Europe to North America - or vice versa - during one of these "hyperthermals".

"There was plenty of life transferring between Europe and North America at that time - mammals, trees - all sorts of things," said Dr Archibald.

"And plenty of insects are similar between British Columbia and Denmark - but they could have lived in a cooler climate and crossed at any time.

"This is the first example we have of something that would have needed warmth in order to make the crossing."


The land bridges across the Arctic would have seen a temperate climate for most of the Eocene, rising during the hyperthermals.

During the course of the research, the team mapped the locations of all ant species, extinct or contemporary, growing longer than 3cm (1.2in).

They found that virtually all are associated with tropical temperatures, although the reason why remains a mystery.

The biggest extant equivalents are the driver ants of the Dorylus genus, found in Central and East Africa, which can also grow to 5cm long. (They are the most dangerous ants in the world)

Driver Ant

Driver Ant

 For more information:

http://www.bbc.co.uk/news/science-environment-13269302

Fire Ants Assemble as a 'Super-Organism' (from Fox News)

The ants may go marching one by one, but they end up forming a superstructure of thousands -- and together they can form a raft that stretches the boundaries of the laws of physics, according to new research released today. 

Ants have exoskeletons that are naturally hydrophobic, or water repellant. A single ant can walk on water because of the buoyancy of the air bubbles trapped next to its body, and the water's own surface tension. However, when thousands of ants stand on top of each other, their multiplied weight should cause them to sink. But for years, biologists have observed fire ant colonies floating down flood plains and rivers in their native South America.

 
For the first time, a group of engineers has attacked the question of ant flotation from a physics perspective. Ants float as a group because they can harness the power of nearby air bubbles. Grasping each other's mandibles or front legs with a force 400 times their body weight, the ants are able to trap small pockets of air between them -- like a group floatation device.

"The ants are so tightly knit together, that air pockets form between the water and the ants, and water cannot penetrate through any part," said Nathan Mlot, a graduate student at the Georgia Institute of Technology in Atlanta and one of the study's authors.

The bottom layer of ants rests on top of the water's surface, and others pile on above them. Even when they do get submerged, the pockets of air bring them back to the surface quickly -- and allow them to breathe. When they get submerged, the ants flex their muscles in unison to form a tighter weave.

To understand exactly how the structure worked, the researchers took a raft of several thousand ants and dropped it in liquid nitrogen, immediately freezing it. Then they were able to look at the structure on an ant-by-ant level under an electron-scanning microscope. "We were surprised at just how waterproof raft was -- its ability to repel water and keep afloat," said Mlot.

What if you want to drown the ants? Just add soap to the water, which greatly reduces its surface tension of water and sinks the raft, said Mlot. "With soap, the ants will drown within a matter of seconds, whereas they can survive for days or even weeks on the raft otherwise."

To test some of the behavioral dynamics inside the pancake-shaped raft, the researchers painstakingly picked ants one by one from the top of the structure. Soon, a new one would climb from the bottom to keep the raft the same thickness.

"We know that self-assembly and self-healing are attributes of living organisms, and we have seen that ant rafts develop these on a macro scale," said Mlot. The study was published today in the journal Proceedings of the National Academy of Sciences.

"Each ant does one tiny job, but they can build these incredible structures," said Kenneth Ross, an entomologist with the University of Georgia who was not involved in the work. Ross says that the rafts include not only worker ants, but also the queen and her brood -- the reproductive cells of the giant superorganism. From what he has seen in his research, the queen usually stays in the center of the raft, with an even tighter ball of ants around her.

This level of social organization isn't common, said Joshua King, an insect ecologist at the Central Connecticut State University, in New Britain. "This study reinforces how unique the collective behaviors of social insects are when compared to other animals."

This type of research could eventually help in many fields, from making a better rain jacket to building robots that can think. When the ants link up their mandibles and legs, they form a highly waterproof weave, which could be the basis for next-generation materials for lifejackets or boats. In addition, social insects like ants have long been the inspiration for autonomous robotics that could link up to build a larger structure.


"Ants are like little computers, acting on a few simple rules of engagement," said Mlot.