Sodanaut

Kelly’s Field Notes

Check out this page from the Mono Lake Committee to see images discussed in this episode.

Common Name: Brine or Shore Flies

Order:  Diptera

Family: Ephydridae (epi “on” hydor “water” = living on the water)

Genera: There are around 130 described genera of brine flies.

Species of Note (There are around 2,000 species of brine flies described!):

• Petroleum fly (Helaeomyia petrolei) - first described in the La Brea Tar Pits, this brine fly’s larvae live in naturally occurring petroleum, feeding off of animal matter found in the petroleum. The eggs are not laid in the petroleum, the larvae hatch and crawl into it. It is the only known insect to develop in crude oil (normally very toxic to insects)!

• Alkali fly (Ephydra hians) - while the adults only live 3-5 days they make the most of it! See below for a longer description of their life cycle.

• Ephydra brucei - found in hot springs, their larvae are subjected to water temperatures exceeding 45 oC (113oF)!

•  Scatella spp. - found in sulphur hot springs.

Description: 

Adult brine flies are fairly small, at 2.5-9 mm in length (0.1-0.4 in). They are generally black or grey in color. Larvae look like classic fly larvae (maggots) though sometimes with greatly reduced heads.

Life Cycle: 

Brine flies live in varied habitats from seashores, to wetlands to hot springs from salt pools to alkaline lakes, even petroleum ponds. Their eggs are generally oviposited (laid) in water though the petroleum fly lays their eggs outside of the petroleum source. For example, adult alkali flies (Ephydra hians) surround their bodies in an air bubble, trapped by waxy hairs all over the fly’s body. The flies do not consume the bubble but use it to move gases into and out of the bubble. Because of this slow gas exchange the fly can remain underwater for up to 15 minutes! They use this time to munch on algae and find a safe spot to lay their eggs. 

Once the larvae hatch (5-6 days after oviposition) they are ready to start eating, while many species eat algae like adults some are predatory like our petroleum fly friend and those of genus Trimerina. In the Great Salt Lake, from April to October/November larvae can consume up to 120,000 tons of algae and organic matter! It takes between 11 and 21 days to reach the pupal stage, which only lasts about 6 days. When ready to emerge, the pupae pulls gases from the lake around itself to form a bubble, the adult emerges into the bubble then floats safely to the surface. Adults live a scant 3-5 days.

If you want to see alkali flies in person, Lake Mono is the place to go! They emerge in large numbers and are a very important source of food for migratory birds passing through as well as residents. The Great Salt Lake also gets billions of flies emerging every year, in such numbers their pupal cases pile up around the shore line. Both Mono Lake and the Great Salt Lake have had significant changes in salinity over the past century that may threaten these unique flies.

Super Powers:

• Flight - like all flies, they’ve got two wings and are ready to fly!

• Chemical Resistance - one species lives most of its life cycle in petroleum, eating the dead arthropods that fall into the pool. Brine flies get their common name for their ability to tolerate salinity which would kill most other aquatic life.

• Walking on Water (or oil) - brine flies can walk on the surface of water due to hairs or glandular secretions on their limbs.

• Diving Bubble - trapping air around their bodies, brine flies can remain underwater for up to 15 minutes at a time.

Brine Flies in Culture:

• The Kucadikadi, part of the northern Paiute people, ate brine fly larvae for the fats and proteins, collecting them from Lake Mono. Kucadikadi means “eaters of the brine fly pupae.” They would dry the pupae then use them in stew.

• The Kucadikadi traded brine fly larvae to other tribes as they were considered a delicacy.

• Mark Twain wrote about the flies in Roughing It. “You can hold them under water as long as you please--they do not mind it--they are only proud of it. When you let them go, they pop up to the surface as dry as a patent office report, and walk off as unconcernedly as if they had been educated, especially with a view to affording instructive entertainment to man in that particular way.”

References:

“Brine Flies | Wildlife | Great Salt Lake Ecosystem Program.” Wildlife.utah.gov, wildlife.utah.gov/gslep/wildlife/brine-flies.html.

Collins, Nicholas C. "Population biology of a brine fly (Diptera: Ephydridae) in the presence of abundant algal food." Ecology 56.5 (1975): 1139-1148.

“Family Ephydridae - Shore Flies.” Bugguide.net, 2024, bugguide.net/node/view/9357. Accessed 20 Dec. 2024.

Frank, Maureen G., and Michael R. Conover. "Spatial and temporal distribution of phalaropes (Phalaropus spp.) and adult brine flies (Ephydra spp.) are linked on Great Salt Lake, Utah." Western North American Naturalist 83.3 (2023): 403-412.

Tatenhove, Aimee Van. “Wild about Utah: The Quiet Importance of Brine Flies.” Utah Public Radio, UPR, 16 Nov. 2021, www.upr.org/programs/2021-11-16/wild-about-utah-the-quiet-importance-of-brine-flies.

Ubulom, Peace ME, et al. "The Oil fly, Helaeomyia petrolei C. 1899, An Innocuous and Unique Dipteran." Nigerian Journal of Entomology, 37 (2021): 114-120.

Wikipedia Contributors. “Ephydra Hians.” Wikipedia, Wikimedia Foundation, 15 July 2022.

Wikipedia Contributors. “Helaeomyia Petrolei.” Wikipedia, Wikimedia Foundation, 28 Oct. 2024.

Wikipedia Contributors. “Mono Lake.” Wikipedia, Wikimedia Foundation, 18 Dec. 2019, en.wikipedia.org/wiki/Mono_Lake.