While it may be tempting to dismiss beetles as just another creepy-crawly bug scuttling through Maine. That would be a huge mistake. Like all the members of the scientific class Insecta, beetles play an important role in the state’s ecosystem.
And beetles also play a big role in the ecosystem in terms of sheer mass, too. Thousands of species of beetles live in Maine alone. But that’s just a fraction of beetles crawling around the planet.
Of all the animals on Earth, 1 in 4 species is a beetle. In other words, a quarter of all species walking, flying, swimming or burrowing around us are beetles.
Beetles by the numbers
Numerically speaking, there are 400,000 known species of beetles on the planet. By comparison, there are a mere 4,000 species of mammals on Earth.
For an entomologist and beetle fan like Bob Nelson, a retired Colby College geology professor, that’s 400,000 reasons to get excited about the taxonomic family Coleoptera.
“There are thousands of species of beetles just in Maine,” Nelson said. “I work with ground beetles like the ones you find when you turn over an old board.
Nelson puts the number of beetle species in the state somewhere between 4,000 and 5,000.
Among the types of beetles calling Maine home are blister beetles, cucumber beetles, carrion beetles, spotted lady beetles, burying beetles and June beetles.
Why there are so many species of beetles in Maine
A big part of the beetle’s success in Maine is they were able to evolve and adapt to a variety of unique environments or microenvironments in the state.
Where you find beetles in Maine depends a great deal on what they eat, how they breed and how they spend their life cycle, Nelson said. Over a millennium, each of those variables has shaped highly specialized beetle species filling its own niche in the ecosystem.
“They are major players in the food chain,” Nelson said. “For example most of the birds in Maine are insect eaters and that includes beetles.”
Other beetles found in Maine, like dung beetles, have evolved to feed on the tiny bits of half-digested grass or other nutrients in the feces of mammals.
“Dung beetles tend to also be specialized,” Nelson said. “Beetles that clean up what a deer leaves won’t clean up after a moose and we need them all to clean up the woods.”
Carrion beetles play a major role in the decomposition of dead animals as they feed on the decaying flesh.
“Some carrion beetles feed only on dead fish, others on small rodents and others are larger dead animals,” Nelson said. “They all fill a special niche taking care of the dead animals on the Maine landscape.”
There are beetles in Maine that live underwater and have gills and other aquatic beetles that live their entire lives in beaver lodges feeding on the fungus that grows there.
Even though honey bees get most of the credit for pollinating plants, Nelson said there are species of beetles that serve as pollinators.
“We would be in a world of hurt if all the beetles suddenly went away,” he said.
An evolutionary success story
Beetles are among the oldest insects on the planet, showing up around 300 million years ago. That’s 234 million years before the first dinosaurs appeared on the scene and a whopping 293 million years before our human ancestors. Whatever evolutionary strategies beetles have employed since then have obviously worked, according to Nelson.
“When you go through the fossil records back to the demise of the dinosaurs 65 million years ago you see that not a single family of beetles has gone extinct since then,” Nelson said. “They all evolved differently and very successfully.”
Correction: An earlier version of this report incorrectly stated that the Asian longhorn beetle is in Maine.