Courtesy Photo / Ned Rozell 
Todd Sformo looks for overwintering insects in the forest near Chena Hot Springs.

Courtesy Photo / Ned Rozell Todd Sformo looks for overwintering insects in the forest near Chena Hot Springs.

Alaska Science Forum: Hardy gnats survive winter half frozen

As sometimes happens in science, a chance decision led to a discovery.

By Ned Rozell

A few winters ago, Todd Sformo was out gathering hibernating insects from the woods near the Fairbanks International Airport. He searched for dead balsam poplar trees, looking for a beetle that spends its winters under the loose bark, exposed to the frigid air.

When he found a few of the beetles and placed them in plastic containers, he noticed thousands of wispy flies sharing space beneath the bark. He collected a few of them, even though he wasn’t sure what they were. He had a few spaces available in a cooling chamber he was using to check the cold tolerance of the beetle, so he thought, “Why not test the mystery insect, too?”

As sometimes happens in science, that chance decision led to a discovery. The second bug, a fungus gnat, survives the winter by allowing half of its body to freeze. The other half, including its head, stays thawed.

“It’s simultaneously freeze-tolerant and freeze-avoiding,” said Sformo, who earned his doctorate at the University of Alaska Fairbanks’ Institute of Arctic Biology in the lab of Professor Brian Barnes. Sformo now works as a biologist with the North Slope Borough in Utqiaġvik.

Most insects that live this far north use one of two strategies to endure the frigid air of an Alaska winter. They either allow their bodies to freeze, removing water from within their cell walls to prevent ice crystals from puncturing them, or they flood their bodies with their own varieties of antifreeze before the cold air oozes over Alaska.

The fungus gnat Exechia nugatoria does both.

Photo by Peter H. Kerr, California Department of Food and Agriculture
The fungus gnat Exechia nugatoria.

Photo by Peter H. Kerr, California Department of Food and Agriculture The fungus gnat Exechia nugatoria.

Sformo uncovered the fungus gnat’s secret while he studied the red flat bark beetle’s incredible resistance to freezing, which shares the fungus gnat’s wintering tree. Sformo and others found that the red flat bark beetle could withstand minus 240 degrees Fahrenheit without perishing. That is a bit of a head-scratcher when you consider the lowest temperature ever recorded on the planet was minus 129 degrees Fahrenheit. Why would a creature invest energy in a mechanism that protects itself from air that cold?

In the lab, Sformo placed the fungus gnats in the same deep-freeze solution into which he lowered the beetles. He chilled the insects until they gave off a spike of heat, an indicator of freezing.

Because he was testing the fungus gnats in the same bath as the red flat bark beetles, Sformo lowered the temperature to an extreme of about minus 100 degrees Fahrenheit.

To his surprise, Sformo found the fungus gnats showed two distinct freezing events, as if different parts of their bodies were freezing at different temperatures.

One part was freezing at about minus 25 degrees Fahrenheit, and something else within them froze at minus 60 degrees below zero. When he warmed the insects back up from minus 25 degrees, most of them came back to life. None survived after dropping to 60 degrees below zero.

Adult fungus gnats look sort of like mosquitoes, with a head and chest (thorax) up front, and a cigar-shaped abdomen behind. Sformo wanted to see if a certain part was freezing before the other, so he snipped in half several fungus gnats.

He found that the abdomens froze at minus 25 degrees Fahrenheit, while the heads resisted freezing until temperatures got to 60 degrees below zero.

Why would a creature allow part of its body to freeze, but not the other? Sformo wasn’t sure, but maybe having part of its body frozen allows a fungus gnat to lose less body moisture to evaporation during the long winter.

Sformo knows a few things about the fungus gnat now—that the insect is surviving cold air like no other known insect, and that some of the most intriguing discoveries in science happen when you are looking for something else.

• Since the late 1970s, the University of Alaska Fairbanks’ Geophysical Institute has provided this column free in cooperation with the UAF research community. Ned Rozell is a science writer for the Geophysical Institute. A version of this column appeared in 2009.

More in News

(Juneau Empire file photo)
Aurora forecast through the week of Dec. 22

These forecasts are courtesy of the University of Alaska Fairbanks’ Geophysical Institute… Continue reading

Denali as seen in a picture distributed by the U.S. Geological Survey in 2015 when the nation’s tallest mountain was renamed from Mount McKinley. (National Park Service photo)
Trump vows name of highest mountain in U.S. will be changed from Denali back to Mt. McKinley

Similar declaration by Trump in 2016 abandoned after Alaska’s U.S. senators expressed opposition.

State Rep. Sara Hannan talks with visitors outside her office at the Alaska State Capitol during the annual holiday open house hosted by Juneau’s legislative delegation on Friday. (Mark Sabbatini / Juneau Empire)
A moving holiday season for Juneau’s legislators

Delegation hosts annual open house as at least two prepare to occupy better offices as majority members.

The U.S. Capitol in Washington, Dec. 18, 2024. The Senate passed bipartisan legislation early Saturday that would give full Social Security benefits to a group of public sector retirees who currently receive them at a reduced level, sending the bill to President JOE Biden. (Kenny Holston/The New York Times)
Congress OKs full Social Security benefits for public sector retirees, including 15,000 in Alaska

Biden expected to sign bill that eliminates government pension offset from benefits.

Pauline Plumb and Penny Saddler carry vegetables grown by fellow gardeners during the 29th Annual Juneau Community Garden Harvest Fair on Saturday, Aug. 19, 2023. (Mark Sabbatini / Juneau Empire file photo)
Dunleavy says he plans to reestablish state Department of Agriculture via executive order

Demoted to division status after statehood, governor says revival will improve food production policies.

Alan Steffert, a project engineer for the City and Borough of Juneau, explains alternatives considered when assessing infrastructure improvements including utilities upgrades during a meeting to discuss a proposed fee increase Thursday night at Thunder Mountain Middle School. (Mark Sabbatini / Juneau Empire)
Hike of more than 60% in water rates, 80% in sewer over next five years proposed by CBJ utilities

Increase needed due to rates not keeping up with inflation, officials say; Assembly will need to OK plan.

Gov. Mike Dunleavy and President-elect Donald Trump (left) will be working as chief executives at opposite ends of the U.S. next year, a face constructed of rocks on Sandy Beach is seen among snow in November (center), and KINY’s prize patrol van (right) flashes its colors outside the station this summer. (Photos, from left to right, from Gov. Mike Dunleavy’s office, Elliot Welch via Juneau Parks and Recreation, and Mark Sabbatini via the Juneau Empire)
Juneau’s 10 strangest news stories of 2024

Governor’s captivating journey to nowhere, woman who won’t leave the beach among those making waves.

Police calls for Wednesday, Dec. 18, 2024

This report contains public information from law enforcement and public safety agencies.

The U.S. Capitol on Wednesday. Funding for the federal government will lapse at 8:01 p.m. Alaska time on Friday if no deal is reached. (Kenny Holston/The New York Times)
A federal government shutdown may begin tonight. Here’s what may happen.

TSA will still screen holiday travelers, military will work without paychecks; food stamps may lapse.

Most Read