Yuen: Seriously, what purpose do mosquitoes serve?

You’re watching the sunset light up the sky with hues of tangerine and fuchsia. It’s a perfect July evening in Minnesota — except for the fiery welts exploding across your thighs, arms and forehead.

This time of year can make the average person feeling existential. But not about human existence. About the existence of mosquitoes.

As in, what purpose do they serve? Do they need to exist?

Matt Aliota said his mom had this nearly identical line of inquiry the night before I reached out to him. They had been sitting out on his deck near dusk and had to move inside after mosquitoes started to feast on them. (“Why don’t we kill them all?” was her question.)

First, let’s just preface Aliota’s answer by saying the University of Minnesota vector biologist is not a bleeding-heart champion of mosquitoes. He knows that their population must be controlled, given that they can spread lethal malaria parasites and dengue virus, which is a threat to about half of the world’s population. Most people who die of mosquito-borne illnesses are children.

“Mosquitoes suck,” the professor acknowledged. “No pun intended.”

But eradication isn’t realistic. And even if it were, Aliota said, “we don’t know enough about how natural ecosystems work to predict what the outcome would be if a single species disappeared.”

I pressed him on the feasibility front. We’ve sent astronauts to the moon, I said. Surely if we put all of our resources behind it, couldn’t we annihilate a public health enemy that surely no one would miss?

Out of the estimated 3,600 mosquito species on the planet, a relative handful — maybe 150 — are capable of transmitting pathogens to humans, Aliota cautioned.

He also reminded me of the history of DDT.

When it was discovered during World War II as a modern synthetic pesticide, scientists believed it would be the silver bullet to eradicate malaria, along with the development of anti-malarial drugs. “But evolution played a role, and now in a lot of places around the world, environmental issues notwithstanding, you can’t use DDT because mosquitoes are completely resistant to it,” he said.

And those environmental and toxicological issues, documented in Rachel Carson’s 1962 book “Silent Spring,” eventually led to its ban in the United States.

Aliota said we need to continue to develop new tools to control mosquito populations. Genetically modifying mosquitoes or infecting them with a particular bacteria are among the emerging technologies. “It’s this ongoing evolutionary arms race between mosquitoes and humans,” he said. “As we develop one countermeasure, they evolve resistance, and it’s this ongoing one step forward, two steps backward.”

OK, now for the main question: Why, oh why, are mosquitoes even on this planet?

Scientists believe mosquitoes have been buzzing around for more than 100 million years. Their earliest ancestors had piercing mouthparts that initially fed on plant fluids and somehow shifted to suck vertebrate blood, possibly dinosaurs, Aliota said.

Turns out, plenty of habitants of Earth would miss mosquitoes if they were suddenly gone today. Bats, birds and other animals eat them. The aquatic larval stages of mosquitoes help recycle nutrients and provide food for fish and other aquatic organisms, he added. Some species of mosquitoes are also pollinators.

So maybe we just need to co-exist.

Both Aliota and I were stunned to learn that this July has had lower-than-average numbers of mosquitoes, according to the Metropolitan Mosquito Control District.

As we itch and groan about their bites, as a reminder, here are the strategies that actually work to protect yourself:

As scientists engage in the arms race against mosquitoes, in the meantime we ordinary humans can find ways to live in harmony with these blood-suckers. Our own arms, perhaps, will thank us.