Staying alive: Rare beetle that uses mimicry to stay ahead of predators shows up in N.B.

If the old saying that imitation is the sincerest form of flattery is true, then willow-leaf beetles in New Brunswick should be feeling pretty good.

A rare adaptation among ground beetles was discovered in Loch Alva, a wilderness area west of Saint John, this summer.

These ground beetles are usually drab and brownish-black, but Don McAlpine found proof that they are mimicking the colourful willow-leaf beetles, which are orange with black-and-white stripes.

The soon-to-retire curator of the New Brunswick Museum was out "beating a willow bush" as he collected insects in a net. His discovery came as part of BiotaNB, a 20 year "biological inventory project" of some of the province's largest natural protected areas.

"I was a little surprised at my net when I found this other beetle," McAlpine said.

"This little beetle, which is very similar in colouration — almost identical in fact to these plant-eating beetles — is a mimic. It mimics the colouration of this beetle to take advantage of it."

McAlpine said the two beetles live side by side because ground beetles live in willow bushes and eat the larvae of willow-leaf beetles.

The ground beetle is "very, very similarly coloured, but it's quite a different shape," he said pointing toward its smaller size and longer neck.

This adaptation has been discovered in other provinces, so McAlpine is not surprised it has shown up here.

Why imitate a willow-leaf beetle?

There are a couple of theories as to why a drab brownish-black ground beetle would mimic a more colourful one, said McAlpine. One has to do with protection.

Over the years, ground beetles have developed an identical physical appearance which will be replicated in future generations.

WATCH | Rare ground beetles found at nature preserve use imitation to stay alive:

Tiny beetles trick predators through mimicry

3 months ago

Duration 1:54

From drab to fab: Ground beetles, discovered in Loch Alva, near Saint John, have adapted to mimic the colourful appearance of willow-leaf beetles.

"A predator is going to encounter one of these [willow-leaf beetles] first and say, 'Not worth my time, jumps too fast,' or, 'Not worth my time, doesn't taste good.' 

"And when it eventually encounters one of these ground beetles, it's not going to bother. It's going to leave it alone," he said. 

McAlpine said his find is the first specimen for New Brunswick and when his team went hunting for the mimics, they found three more.

Other mimics in nature on display

The New Brunswick Museum has examples of mimicry in other species.

McAlpine points to viceroy butterflies that have, over time, started looking like monarchs.

He also has a display of five different kinds of bees, a wasp, and a flower fly, that all resemble one another.

He said the wasp and the bees all sting. The flower fly does not, but from a predator's eye they would all appear the same.

"It takes advantage of the fact that these fellows here do sting and they often occur at the same flowers together," he said. 

"So if you see this little flower fly or syrphid, you're probably going to leave it alone thinking that 'No, it might sting me.'"

McAlpine said mimicry also occurs in frogs and snakes, and some species of flowers like orchids use mimicry to look like insects in an effort to attract pollinators.

He said these examples of the ground beetle will remain in the museum's collection. 

Beetles have been extensively studied in the province over the last couple of decades, however there is always more to learn, he said.

"I think it's just an indication that there are still lots of interesting things to find out there that we don't know."