Giant Ant Queen Fossil Suggests Insects had Higher Tolerance to Cold Weather, Experts Say

According to experts, the fossils of a giant ant queen show that earlier insects had a higher tolerance for cold temperatures.

Huge carnivorous ants swarmed the North American prehistoric forest floors nearly 50 million years ago in search of food.

Queens the size of hummingbirds presided over some prehistoric colonies that existed in what is now the state of Wyoming.

Giant Queen Ant

Even bigger ants than those have never walked across the surface of the Earth. The biggest recorded ant queen was a relative that was discovered in fossil form in Germany. She measured more than 2 inches in length, had wings that spread out over 6 inches, and had the body mass of a wren. It is believed that her army of workers hunted anything that got in their way, possibly even lizards, birds, and mammals.

These ancient insects were probably ectothermic, which means they struggle to survive in the absence of a significant amount of heat in their surroundings, like modern ants. Their body size has a significant impact on how low the temperature can go before they stop thriving.

Animals that can regulate their own body temperature can endure colder climates by increasing their mass and decreasing their skin, whereas animals that must absorb heat from their surroundings benefit from having greater surface area and less volume. For instance, larger ant queens are now found nearer the tropics.

Tolerance to Cold Weather

Researchers hypothesized that this temperate land bridge once had a climate-controlled "gate" in their paper published in The Royal Society in 2011. That door may have opened briefly during intervals of global warming, making it possible for ants and other organisms with cold blood to move freely between continents.

That theory is now complicated by the recent discovery of an ancient giant ant queen's fossil.

It too is a member of the Titanomyrma genus, which also includes the enormous ants that can be found in Wyoming and Germany.

However, this one was discovered in British Columbia, Canada, making it the first fossil of this type to be discovered in such a harsh environment.

Due to its compressed state, scientists are unsure of its size, yet there is a chance it was as large as its Wyoming counterpart.

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Insect Size vs. Weather

The Canadian Titanomyrma cannot be categorized into a specific species because of its poor condition, but it is similar in age to other fossil records of its kind discovered in Wyoming and Europe.

The organism was originally 3 or 5 centimeters long, depending on the direction of compression.

The smaller estimate would reduce it to a size that is 65% smaller than that of its Wyoming counterpart, which supports the theory that giant ants can only pass through the climate gate of the Bering land bridge during times of global warming.

The larger dimension suggests that these ancient giant ants could have managed to cross the land bridge at any time and had greater cold tolerance than previously thought.

The only way to differentiate between those scenarios is to find more fossils, Science Alert reports.

The study by Archibald and his colleagues was published last month in The Canadian Entomologist.