Battle Hymn of the Floodwater Mosquito

The eggs sit patiently in the moist soil, waiting for the river to rise. They are tiny things, not even a millimetre long, dotting the banks of the Fraser River from Vancouver to Hope and beyond in the millions. Their mothers will never meet their young, but they have one gift to pass on: a carefully selected resting place where the eggs can survive for years.

When warm weather hits, the snowpack melts, releasing a winter’s worth of water into a river that will rapidly rise. The moment the water touches the eggs, they know what to do. It takes only minutes after inundation for the larvae to hatch, and a new generation of floodwater mosquitoes is born.

I am a city boy from Vancouver who hasn’t seen much of the province. The mosquitoes we get here hang out in urban parks. They’re a mild nuisance, but nothing to ruin your day. I knew nothing of the insects that lived upriver, thriving in the water margins and feeding on blood in this part of the world for millennia.

That changed when I visited Sea Bird Island. I was sent to interview a grain farmer on the island, which sits in the middle of the Fraser River not far from Harrison Hot Springs. Farmer Jim took me around the property to admire his organic wheats, oats and rye. It was a beautiful spot, with the stalks growing against the majestic backdrop of Mount Cheam. But then the truck passed a slough.

It was June. The peak of the spring freshet had already arrived, filling the tree-lined slough with water, rousing the clutches of eggs the moment they detected a lack of oxygen, to become buzzing adults in 10 days or so. There are two species of floodwater mosquitoes that make their home on the Fraser: Aedes sticticus and Aedes vexans. Both feast on mammals like me.

It was a hot day so we had the windows half down in the truck. That meant that the mosquitoes could fly in but had a hard time flying out. About two dozen were trapped with us in the truck, hovering and humming, each with six spindly legs poised to land on my skin.

Mosquitoes have myriad ways to detect humans: the heat from our bodies, the odours from our skin, the carbon dioxide we exhale. With every breath, they knew I was alive and where I was.

The hunters in the truck were all female. It is the mothers-to-be who are after our blood, which is full of proteins, iron and amino acids to nourish their eggs, which they can lay 100 at a time. They flew under the cuffs of my trousers, pierced my skin and drank deeply from my legs.

I returned to Vancouver covered with the pinkest, puffiest bites. While they covered my legs, the worst were the ones on my fingers, itching as I typed my report from Sea Bird Island on the keyboard.

Curious whether it was the city boy in me who couldn’t handle some floodwater mosquitoes, I asked Tribal Chief Tyrone McNeil, who is Stó:lō and a member of Seabird Island Band near the farm I visited, about his run-ins.

“I was gardening and have high tolerance. But one year, they were horrible,” he told me. “The ’sqitoes drove me inside my home, where I grabbed my camera.... I took a picture of the front and back of my hand and counted 28 on the palm side and 37 on the back.”

OK, so it wasn’t just me. The experience gave me newfound fascination for the creatures and I think of them whenever I’m near the Fraser.

Driving along the river’s mouth here in Vancouver and Richmond, I see new neighbourhoods of condos erected along the water. The developments have names like River District and Parc Riviera. There are no mosquitoes mentioned in the pre-sale ads even though the river is more their home than ours, living in greater density than any tower of residents set to go up.

Even with our attempts to shape the river, the places where the water meets the land will always be mosquito territory. Do we resist or do we retreat?

A long history of blood feeding

The mosquito is ancient.

It might be the stories of great floods and colonial expeditions that are the best known in our province, but look deeper into Indigenous oral histories and settler accounts, and you’ll find that the creature has always been buzzing about.

There is a Tsimshian tale about a mosquito chief with a proboscis of pure crystal. In a Kwakwakaʼwakw tale, Dzunuḵwa, the wild woman who eats children, is tricked into a firepit, her ashes turning into mosquitoes.

One place that bred endless swarms was the shallow shores of Sumas Lake, a spillway of the Fraser River. The Semá:th people depended on its environment almost entirely for food, but even they could not contend with the numbers.

People kept fires to ward them off, bound their legs in cloth and strips of cedar and built stilt huts out on the lake, as the insects did not stray from the shore. But people would also leave the lake entirely to escape the swarms. The name of one encampment in the Halkomelem language is Tehm-eh-kwiy-ehl, which means “at mosquito time.”

Despite its nuisance, the Semá:th people respected the creature, with warriors adopting it as a spirit helper on the eve of battle in hope of possessing its powers.

When settlers arrived, they were in for a shock.

One of the earliest mentions of mosquitoes comes from the 1808 diary of explorer Simon Fraser. It is fitting that he would complain about them, considering that the river lands the insects call home would later bear his name. “Musketoes,” he wrote, “are in clouds.”

The first European farmers that came along to the Fraser Valley reported that mosquitoes killed their dogs and calves.

“One reputable gentleman maintains that he had in his possession at one time a cow whose tail had been so bitten by these venomous pests that it dropped off,” wrote Thomas Crosby, a missionary who documented his life in the 1860s and ’70s.

During a stay in Langley, Crosby lit a candle in the night. It quickly turned “black with dead insects.”

Hunting the hatching hunters

Over the decades, wetlands have shrunk as humans dike and urbanize along the Fraser River. One estimate says that colonization has reduced them to 10 to 30 per cent of their original area. Nonetheless, the mosquitoes are still hunting us.

Dirk Lewis hunts the hunters. It all started with a high school job doing pest control. He would venture into Abbotsford backyards at night like a Ghostbuster, spraying organophosphate from a motorized backpack while trying not to trip over garden hoses.

“It wasn’t a very effective strategy,” said Lewis, who remembers accidentally triggering many a yard sprinkler in the dark. “The organophosphate would kill the mosquitoes in that backyard, but then the winds would shift and the mosquitoes would come from every other backyard.”

He made a career of it and is now the lead biologist at Morrow BioScience, which has been running mosquito control programs for local governments in B.C. since 1984, as well as a 24-hour mosquito hotline.

Governments have deemed the creatures “nuisance mosquitoes,” but just what that constitutes is a difficult thing to measure. An old study says three bites on an exposed forearm in a minute is too much, says Lewis, but that also depends on who you are.

“You’ll have somebody who moved into a rural area and they’ll find mosquitoes off-the-charts annoying. But I’ll be talking to a farmer who’s been on that land with their family for over a hundred years and they’re not even batting an eye.”

There are financial implications too, he says, everything from golf courses with too many swarms to attract golfers to produce farmers who are attacked so aggressively that they cannot do their work.

The province is now the backyard in which Lewis does his work. But he and his team have much more effective ways of fighting their seasonal surge than the organophosphate of his teenage years.

The Fraser, like all of the province’s great rivers home to mosquitoes, is one that needs to be closely monitored. The river runs through the municipalities of the Metro Vancouver and Fraser Valley regional districts, both of which have employed the firm to control mosquitoes.

As soon as the weather warms and snowmelt hits the river, the race begins. When the millions of mosquito eggs release larvae into the water, the team needs to kill them in the week before they turn into pupae, their next life stage.

They hustle to the riverbanks on foot and by boat, getting to the water underneath heavy cottonwood trees and thorny blackberry canes where larvae have hatched.

In 350-millilitre samples of water they’ve scooped from the river at this time, Lewis sees between 1,000 and 2,000 larvae.

“They’re extraordinarily successful,” he said. “All of the water that’s flooded in is writhing in black mosquitoes.”

By hand or with backpack spreaders, they distribute a special kind of corn granule. The granules carry Bti, a natural soil-borne bacterium that is fatal to larvae, and only four kilograms is needed per hectare of water to be effective. In years when there have been especially high-water areas of the Fraser, they’ve used helicopters.

“The goal for us is to get the biggest bang for our buck, to get the most larvae possible within the application window,” said Lewis.

But that can be tricky depending on the temperature from year to year. If there’s sudden heat and the snowpack melts quickly, this creates one big spike in water levels, waking up all the mosquito eggs at once. The team can then wade in with one round of treatment. But if the snowpack melts slowly, keeping the water level high for weeks, the team will have to return to the river again and again to kill each wave of larvae.

They use their phones to log where the mosquitoes are every time they’re out in the field. That data is collected into software that plots it on a map, what life stage they’re in relative to water levels and what that looks like over time.

“We hope that this is going to give us some predictive capabilities,” said Lewis.

The firm is also waiting for their provincial drone certifications to come through so that they can start flying them out onto the river to apply larvicide. Helicopters guzzle fuel, are often reserved for firefighting and might come up against wind when trying to spread the corn granules. Drones are nimbler, and Lewis is eyeing one that can carry over 50 kilograms that would be able to cover 10 hectares in nine minutes.

“We’re trying to cut our footprint,” said Lewis. “This will allow us to be a little more light.”

A spot of water, a lot of bother

There’s a theory from mosquito experts that when the Sahara, once grasslands, dried into a desert 13,000 years ago, yellow fever mosquitoes were driven into human villages. They learned to survive in containers of water and, while living near people, developed a taste for human blood.

It’s a lesson for us in the flood plains of the Fraser Valley. Altering mosquito habitat doesn’t necessarily mean getting rid of mosquitoes, says Ben Matthews, an associate professor of zoology who runs the Mosquito Lab at the University of British Columbia.

“Instead, you might shift the balance of different species,” he said. “You might provide habitat for different mosquitoes that are pre-adapted to hanging out with humans. A lot of them will breed not in rivers or lakes or natural bodies of water, but in containers, clogged gutters or bird baths. They’ve developed an affinity for the small volumes of water that we leave behind as we go about our daily lives.”

That’s why local governments will issue summertime warnings for residents to remove or refresh standing water on their property, everything from animal troughs to kiddie pools to old tires.

You never know where they might survive.

A colleague of Matthews’ in Calgary found the Culex pipiens species in the dead of winter, thriving in the warmth of parkades. As for Lewis the mosquito hunter, who lives in Rossland, it took him two years to find the source of the mosquitoes that prevented him from sitting on his back deck: a discarded fireplace on the edge of his neighbour’s property that happened to be collecting a little bit of water. His mantra: “It doesn’t take a very big spot of water to create a lot of bother.”

A species named Aedes togoi has been laying eggs in the rock pools along the coast in places like West Vancouver’s Lighthouse Park. These are not tide pools with fish that would eat mosquito larvae, but tiny pools formed from rainwater and salt spray. The research showed that the species can survive in extremely salty water.

It’s surprises like these that make studying this tiny insect rewarding for Matthews.

“They’re an incredibly diverse set of species,” he said. “Understanding how they interact with human civilization and how their biology has allowed them to survive all these different environments is something that I find endlessly fascinating.”

Migration, misinformation and mozzies

With climate change, the habitat of mosquitoes in Canada could look very different in the near future.

“They might be totally fine in the summer if they happen to hitchhike with somebody’s car or a truck or a boat or a plane,” said Matthews. “But then the population can’t establish itself because all of the eggs will die out over the winter. So as winters get milder, that’s potentially going to be one less barrier for them to move further north.”

Mosquitoes like Aedes albopictus and Aedes aegypti have already been detected in southern Ontario. The former is currently being monitored by the Public Health Agency of Canada.

“Those are the two big vectors that are on people’s minds, because they can transmit yellow fever, dengue, Zika, chikungunya,” said Matthews. “They’re really good at invading new territory.”

At Lewis’s firm, aside from having to deal with the shifting hydrology of the Fraser River in the face of climate change, there’s also misinformation.

Mosquito control, by nature, is polarizing work. Lewis recalls how the corner store of one community became the place to sign petitions both for and against control. But it’s gotten worse.

One conspiracy he’s heard in the Lower Mainland, though more so in rural communities, says that governments are seeding clouds to create more snow on the mountains, which is intensifying the freshet and causing more mosquitoes. There’s also distrust in pesticides, with people believing that companies and regulatory bodies are not telling the public about harmful inert ingredients they contain.

“There’s a very large distrust of science and a very large distrust of government,” said Lewis. “A lot of times where I sit, I get that Venn diagram where those two distrusts overlap in the middle: we rely on the science that tells us that the pesticides we’re using are effective and safe, and we work for governments that would like us to do this work. It’s really difficult.”

Nice and juicy

There’s nothing like strolling Richmond’s dike trail and catching the sunset at the mouth of the Fraser River, an orange horizon stretching over the slow waters. No matter how hot the summer is, I wear long sleeves and long pants on these walks. After learning so much from the Mosquito Lab, I have no choice but to accept that I’m going to be hunted.

“When people talk about intelligence and insects, you get into some interesting debates about how smart can they be,” said Matthews. “What I tend to say when talking about mosquitoes is that it’s sensory specialization.”

The Mosquito Lab’s specialty is neuroscience, and they use tools like the calcium imaging and the genome editing tool CRISPR-Cas9 to look at how mosquito neurons are activated by chemical cues like our skin odours. Aedes aegypti, for example, was shown in a study that Matthews worked on to prefer humans to animals even if both are around.

We’re just “really nice, juicy targets,” he said.

“Evolution has crafted them into being really potent hunters. They’re not like honeybees, which go out, identify a food source and come back to a hive to dance and tell all their friends about it. Mosquitoes tend not to live socially and do things like that. That doesn’t mean they’re not smart, but in my mind it’s more about shaping their nervous system to be extremely sensitive and extremely responsive.”

Summer is coming to an end, but the mosquitoes have taught me to keep an eye on how we’re changing the river and changing the climate. Next year’s eggs are already lying in wait. Once they hatch, I know they’ll come say hi.