Scuba flies

In California’s Mono Lake — whose alkaline waters are deadly to most insects — these diving flies don’t just survive; they thrive.

 

This story was originally published by bioGraphic, and is reproduced here with permission. 

From a distance, it looks like a landscape from another, rather inhospitable world: Bulbous limestone towers rise from the glassy surface of a lake with seemingly barren shores, and the craggy mountains in the background add an exclamation point to the unwelcoming scene. Analyzing a sample from the lake would do little to alter this impression—the water here is nearly three times saltier than the ocean and, with a pH of 10, far more alkaline. Upon closer inspection, however, it becomes exceedingly clear that California’s Mono Lake teems with life. Alkali flies (Ephydra hians) clamber over every available surface—both above water and below—and they draw millions of nesting and migratory birds searching for a nutrient-rich food source.

To survive in this harsh environment, the flies perform a feat that Mark Twain described with great fascination in 1872. “You can hold them under water as long as you please—they do not mind it—they are only proud of it,” he wrote in a passage of his book Roughing It. “When you let them go, they pop up to the surface as dry as a patent office report.”

Despite both that colorful description and the critical role that alkali flies play in Mono Lake’s surprisingly productive ecosystem, very little was known about the insects’ scuba-diving prowess until biologist and engineer Floris van Breugel, then at Caltech, set out to study them in 2015.

naturepl_floris_20170606_0205-jpg
Floris van Breugel

“There are carpets of flies now,” says van Breugel. “And apparently a couple hundred years ago, it was even more insane.”

naturepl_20150614_0070-jpg
Floris van Breugel

The local Native people, the Kutzadika'a (which loosely translates to “fly-eaters”), used to harvest the high-fat, protein-rich pupae and eat them like rice.

naturepl_20160722_0663-jpg
Floris van Breugel

What most intrigued van Breugel, though, was the flies’ ability to punch through the surface tension of the lake, walk underwater to eat algae and lay their eggs, and then emerge unscathed from conditions that would kill most insects.

naturepl_20150611_0297-jpg
Floris van Breugel

Using a combination of force measurements, manipulations of water chemistry, high-speed video, and scanning electron microscopy, van Breugel and Caltech bioengineer Michael H. Dickinson discovered how they do it.

To begin their dives, alkali flies plunge headfirst into the water and pull themselves down with powerful legs capable of exerting a force at least 18 times their own body weight.

naturepl_alkali_fly_2-jpg
Floris van Breugel

A dense coat of waxy, water-repellant hairs traps a layer of air around an alkali fly’s body as it dives beneath the surface.

naturepl_floris_mono_20170605_0026-jpg
Floris van Breugel

The resulting air bubble doesn’t just protect the fly from Mono Lake’s caustic water; it also functions as an external lung, continuously pulling oxygen out of the water via diffusion as the fly breathes. Thanks to this built-in scuba tank, the flies can crawl to depths of 8 meters (26 feet) and remain submerged for up to 15 minutes.

naturepl_floris_mono_20170611_0984-jpg
Floris van Breugel

The lake’s iconic tufa towers, which are created when calcium-rich, underwater springs react with minerals in the water, also contribute to the flies’ success. While some are visible above water today—the result of tributary diversion by the city of Los Angeles for municipal water and hydroelectric power—many more remain beneath the lake’s surface.

naturepl_floris_mono_20170609_0558_pano-jpg
Floris van Breugel

The porous limestone accumulations provide the flies with grippy surfaces on which to cling while underwater, allowing them to stay submerged even while towing a buoyant bubble of air. They also offer countless protected nooks and crannies in which female flies can lay their eggs.

naturepl_20150928_1077-jpg
Floris van Breugel

Both adult flies and their larvae are critical food sources for the nesting and migratory birds that spend time at Mono Lake each year, many of which depend on a refueling stop at the lake to sustain them during long journeys.

naturepl_20150730_0647-jpg
Floris van Breugel

Since the flies provide more fat and protein than brine shrimp (Artemia monica), Mono Lake’s other main food source, the insects are the food of choice for most of the nearly 100 species of birds that visit the lake.

naturepl_20150928_1056-jpg
Floris van Breugel

In 1994, the California Water Board ruled to amend the licenses that had allowed water to be diverted from the lake. Without that ruling, says van Breugel, it’s possible that the ecosystem could have collapsed, and we may never have learned how something as seemingly insignificant as the arrangement of hairs on a fly can impact millions of migratory birds. “It makes you realize how important such tiny little things can be on the global scale.” 

High Country News Classifieds
  • WESTERN WATER PROJECT MANAGER
    National Wildlife Federation is hiring NM-based position focused on riparian corridors, watershed health. Learn more and apply online: https://www.nwf.org/about-us/careers
  • ASSOCIATE PROGRAM DIRECTOR
    Position Title: Associate Program Director Location: New Mexico; flexible in state Position reports to: Senior Program Director Position Closes: March 13, 2020 GENERAL DESCRIPTION: The...
  • DEAN, W. A. FRANKE COLLEGE OF FORESTRY AND CONSERVATION, UNIVERSITY OF MONTANA
    Dean, W. A. Franke College of Forestry and Conservation, apply http://bit.ly/2548umjobs. AA/EEO/ADA/Veterans Preference Employer
  • GRAPHIC DESIGNER
    Western Resource Advocates (WRA) seeks a creative and driven graphic design professional to design high quality print and digital collateral. The Graphic Designer will bring...
  • STEWARDSHIP SPECIALIST
    San Isabel Land Protection Trust seeks experienced person to manage its 133 conservation easements in south-central Colorado.
  • CAMPAIGN REPRESENTATIV
    Sierra Club's Beyond Dirty Fuels Campaign is hiring an experienced campaigner to lead our work challenging the oil and fracked gas industry on the Gulf...
  • AG LANDS PROGRAM DIRECTOR
    Oregon Agricultural Trust (OAT) seeks passionate relationship builder experienced in coordinating agricultural conservation easement transactions.
  • REMOTE SITKA ALASKA FLOAT HOUSE VACATION RENTAL
    Vacation rental located in calm protected waters 8 miles from Sitka, AK via boat with opportunities to fish and view wildlife. Skiff rental also available.
  • FINANCE DIRECTOR
    Mountain Studies Inst (MSI) is hiring 4+ positions: Finance Director; Coms/Engagmnt Mngr; Dev/Engagmnt Dir; Americorps vol
  • COMMUNICATIONS AND ENGAGEMENT MANAGER
    Mountain Studies Inst (MSI) is hiring 4+ positions: Finance Director; Dev/Engagement Dir; Coms/Engagement Mngr; & Americorps volunteer
  • SEASONAL TRAIL CREW LEADERS
    Lead the nation's premier volunteer-based trail crew programs on the spectacular Pacific Crest National Scenic Trail. This is a great career-building opportunity for rising professionals....
  • ORGANIZING AND TRAINING COORDINATOR
    Is this your dream job? Are you looking to join a nationally recognized organizing network, live in a spectacular part of the West, and work...
  • DEVELOPMENT AND ADVOCACY DIRECTOR
    Provide stewardship and protection for the Great Burn wildlands along the Montana-Idaho stateline. This position is based in Missoula, MT, where a river runs through...
  • EXECUTIVE DIRECTOR
    Central Oregon LandWatch is seeking an Executive Director to advance our mission and oversee the development of the organization. Job Description: The Executive Director oversees...
  • LISA MACKEY PHOTOGRAPHY
    Fine Art Gicle Printing. Photo papers, fine art papers, canvas. Widths up to 44". Art printing by an artist.
  • SAN JUAN BASIN ENERGY CAMPAIGN ORGANIZER
    San Juan Citizens Alliance is seeking a full-time San Juan Energy Campaign Organizer located in Farmington, New Mexico. The San Juan Energy Campaign Organizer focuses...
  • WILDLIFE PROGRAM MANAGER
    San Juan Citizens Alliance (SJCA) is looking for a passionate, experienced, and motivated Wildlife Program Manager to lead campaigns to protect and enhance wildlife and...
  • GRANT WRITER
    "This thriving citizens organization exemplifies the ideal of public involvement in public processes."- Billings Gazette Help protect Montana's water quality, family farms and ranches, &...
  • COMMUNITY ORGANIZER AND MEMBERSHIP COORDINATOR
    Western Colorado Alliance is hiring for 4 positions, 2 Full Time Community Organizers, 1 Part Time Community Organizer and a Part Time Membership Coordinator. For...
  • BUSINESS OPERATIONS DIRECTOR
    Thorne Nature Experience is looking for a Business Operations Director who will work in partnership with the Executive Director and Thorne's Directors and Managers to...