Nestled at the foot of California’s eastern Sierra Nevada, Mono Lake looks like it belongs on another planet. Its shoreline is dotted with bizarre, spindly formations called tufa towers. The water glows an unnatural blue-green. It smells faintly of minerals and salt. It’s so salty and alkaline, in fact, that fish can’t survive in it. Yet this seemingly inhospitable place is a thriving oasis—thanks in part to one of the most remarkable insects on Earth: the Mono Lake brine fly (Ephydra hians).
These flies are more than just bugs buzzing at the water’s edge. They’re underwater foragers. Air-bubble divers. And critical links in one of the most unique food chains in North America.
A Harsh Habitat
Mono Lake is what’s called a terminal lake—it has no outlet. Water flows in from mountain streams, carrying minerals with it, but never flows out. Instead, the water evaporates, leaving behind increasing concentrations of salt and alkaline compounds like sodium carbonate, borax, and arsenic. Today, Mono Lake is roughly three times saltier and over 80 times more alkaline than the ocean.
These conditions make it hostile to most life. No fish can survive here. But two native invertebrates have evolved to thrive: brine shrimp (Artemia monica) and the unsung hero of this story—the brine fly.
Meet the Diving Fly
The Mono Lake brine fly is about the size of a sesame seed. It might look ordinary at first, but its behavior and biology are astonishing.
Unlike other flies, Ephydra hians routinely dives underwater to feed. It walks down the rocky lake edge or clings to submerged tufa towers, fully submerging itself for minutes at a time. Under the water, it scrapes up microbial films and algae that grow on submerged surfaces.
And here’s the incredible part: the fly does all of this while wrapped in a shimmering air bubble, like a tiny diver in a glistening silver wetsuit.
The Secret to Survival: The Bubble Suit
The fly’s “bubble suit” is not just for show—it’s a marvel of natural engineering.
As it dives, the fly traps a layer of air against its body using specialized, ultra-water-repellent hairs. These hairs are arranged in nanoscale structures that create a cushion of air.
This bubble does three key things:
- Protects the fly from the caustic water, preventing salt and alkaline compounds from damaging its tissues.
- Provides a breathable layer of oxygen, allowing the fly to “scuba dive” beneath the surface.
- Maintains buoyancy and mobility, enabling it to crawl and feed efficiently underwater.
Researchers studying these flies have found that their water-repellent capabilities rival advanced synthetic materials. Their nanostructured hairs inspired designs in biomimetic engineering and have been compared to high-tech water-resistant coatings.
In a 2017 study published in PNAS, scientists from Caltech and UC Berkeley described how these flies can dive and re-emerge without salt crusting on their bodies, even after dozens of dives—a feat no lab-made material has yet matched.
Life Beneath the Surface
So what do these flies eat? Their diet consists mostly of algae and microbial mats that coat submerged rocks. This organic matter would otherwise build up and rot. By feeding on it, the flies help keep the lake clean and balance the microbial ecosystem.
They live as larvae in the shallows, eventually pupating and emerging as adults during Mono Lake’s warm seasons. Adult brine flies are short-lived—living just a few days—but their sheer numbers are staggering. During peak summer, the lake’s edges are swarmed with millions of brine flies.
These massive swarms don’t bite, sting, or spread disease. Instead, they serve a vital ecological role.
A Bird Buffet
Mono Lake is a vital stopover along the Pacific Flyway, a major migratory route for birds traveling between North and South America. Over 2 million migratory birds visit the lake each year, and many depend almost entirely on brine flies (and brine shrimp) for food.
Birds like the Wilson’s phalarope and eared grebe time their migrations with the fly hatches. Phalaropes spin in circles on the water to stir up brine flies, then snap them up by the thousands. Grebes dive for fly pupae and shrimp, fattening up before long, nonstop flights to South America.
Without the brine fly, this crucial stopover would be a biological desert.
A Threatened Balance
But this unusual ecosystem has been on the edge of collapse.
In 1941, the Los Angeles Department of Water and Power began diverting streams that fed Mono Lake to supply water to the growing city. Over the following decades, the lake’s surface dropped more than 45 vertical feet, losing half its volume. As water levels fell, salinity and alkalinity rose, putting immense stress on the lake’s fragile invertebrate populations—and by extension, the birds that relied on them.
By the 1980s, alarmed scientists, conservationists, and birders rallied to save the lake. Their work led to the formation of the Mono Lake Committee, which launched a successful legal campaign against the water diversions. In 1994, the California State Water Resources Control Board ordered that stream flows be restored to help refill the lake and stabilize its ecosystem.
Today, the lake is slowly recovering. It hasn’t yet reached its ideal sustainable level, but the brine flies and the birds are holding on—thanks to decades of dedicated advocacy.
More Than Just a Fly
The Mono Lake diving fly is more than a curious footnote in entomology. It’s a symbol of biological ingenuity, resilience, and ecological interdependence. It’s a creature that reminds us that life can adapt to the harshest of environments—but only if we protect the conditions that make that adaptation meaningful.
As climate change alters rainfall patterns and pressures mount on freshwater systems across the West, Mono Lake’s future is far from secure. But the diving fly’s existence continues to inspire awe—and a call to action.
What You Can Do
At EcoServants®, we believe stories like this are worth sharing—and protecting.
- Learn more about threatened lake ecosystems.
- Reduce your own water and plastic footprint: https://ecoservantsproject.org/plastic-footprint-survey
- Volunteer to support habitat preservation efforts: https://ecoservantsproject.org/volunteer-intake
- Explore internships that empower conservation through science and storytelling:
https://ecoservantsproject.org/intern-opportunities/#intern_form