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A fossilized giant horntail wood-wasp is shown in a rock discovered by Bruce Archibald.HO-Royal BC Museum/The Canadian Press

It was literally a huge discovery.

Bruce Archibald was searching for fossilized insects in British Columbia's southern Interior when he cracked open a rock and found a beautifully-preserved giant horntail wood-wasp.

"I immediately jumped up and split my pants," he recalled with a laugh. "Probably, the species should have been named Latin for pants-splitter, but we went with something a little more technical."

Archibald, a paleoentomologist with the Royal B.C. Museum and Simon Fraser University, had discovered a 53-million-year-old species of giant wasp, which he dubbed Ypresiosirex orthosemos.

The insect, seven centimetres in length, is one of three new wasp species that Archibald and Alexandr Rasnitsyn of the Russian Academy of Sciences identified in an article published online in The Canadian Entomologist.

While most B.C. hikers would be somewhat alarmed to encounter a wasp of that size, the ancient wasp was actually only slightly larger than its modern descendants.

"They're pretty big pests of forests today," said Archibald. "The interesting part is that it's so close to its modern relatives. So when you put it in a forest 53 million years ago with very different conditions ... you can see how their community responds."

Today, young horntail wood-wasps bore tunnels through wood to grow fungus that they eat. The fungus emits poisons while the wasps produce a secretion that weakens the tree's immune system, eventually killing it.

Archibald discovered the ancient species in the McAbee Fossil Beds near Cache Creek. The other new species were also found at the site.

Archibald said the discovery gives researchers insight into how the modern world started to come together after the extinction of the dinosaurs. All the elements enjoyed by today's giant horntail wood-wasps were in place 53 million years ago — including trees such as fir, pine, spruce, hemlock, sequoia and cedar.

Further, the species also tells researchers about what kinds of plants and animals live together when the climate is warmed up slightly. He described the winter weather at that time as similar to that of present-day Vancouver but with few — if any — days of frost.

That meant the horntail wood-wasp, which prefers a temperate climate, was living alongside creatures that prefer tropical weather, including a species of cockroach that is now only found in Fiji.

"People often ask me, 'Why should I care what fly flew in the sky 53 million years ago?"' Archibald said.

"What I say is: the more that we understand about the origin of our modern forest ecosystems, and the more we understand about how plants and animals respond and how the communities changed in different climates, the better off we're going to be as we move into the future."

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