Bug’s ‘mind-boggling’ ability to create heat to avoid freezing to death

By Stephen Beech

An insect has the "mind-boggling" ability to generate its own heat to avoid freezing to death, reveals new research.

Snow flies can produce bursts of heat as well as antifreeze proteins, say scientists.

They investigated how the tiny, wingless insects - that crawl across snow to find mates and lay eggs - are able to survive in freezing cold temperatures.

The team discovered that the snow-dwelling fly uses a combination of strategies - generating its own body heat like a mammal and producing antifreeze proteins like an Arctic fish.

While sub-zero temperatures are a death sentence for most other insects, the specialised adaptations allow snow flies to remain active at temperatures as low as -6 degrees Celsius (21.2 degrees Fahrenheit).

The study, published in the journal Current Biology, sheds new light on how life has adapted to survive in extreme environments.

The researchers say their findings could potentially help develop new ways of protecting cells, tissues and materials from cold damage.

Study co-leader Professor Marco Gallio, of Northwestern University, Illinois, said: “Insects are cold-blooded, so they are at the mercy of external temperatures.

“But they have a mind-boggling ability to adapt to extremes.

"When it gets cold, a common strategy is to find shelter and become dormant until conditions get better.

"But instead of slowing down, snow flies actually prefer freezing cold, snowy conditions and hide away when the snow melts and it gets warm.

"They really push the limit of what’s possible.

"Now we’ve found snow flies aren’t just tolerating the cold, they have multiple ways to counteract it.”

He explained that before scientists can understand an organism’s unusual behaviour, they need to uncover its biological tools.

To do so, Gallio and his team became the first researchers to sequence the snow fly’s genome.

They then compared it to that of related insects that are not specialized to withstand cold.

After analysing the fly’s full genome, the team then studied its RNA, which provided information about which genes the fly actually uses to survive the cold.

Gallio said: “We couldn’t find many of the genes within any database.

“Initially, I thought we must have sequenced some alien species.

"It’s very rare for an active gene, which makes a protein, to not have a match.”

Eventually, the team realised the mysterious genes produced multiple antifreeze proteins.

Similar to antifreeze proteins found in Arctic fish, Gallio explained that the snow fly’s proteins bind to ice crystals to prevent them from growing.

The ice shield protects cells from damage caused by freezing.

More from this section

+5

New polish helps people with long nails use touchscreens

Over 400 million barrels will be added to the oil market soon – what are strategic reserves and what can they do?

+2

Is peer pressure more online in 2026?

Gallio said: “Remarkably, some of the antifreeze proteins we found are actually structurally related to those of Arctic fish.

“That suggests evolution came to the same solution for a common problem.”

The researchers also found an unusual set of genes tied to energy use and cellular processes associated with heat generation.

Together, those genetic clues suggested that not only does the snow fly resist freezing, but it also generates its own heat.

Gallio said: “We found genes that in larger animals are associated with mitochondrial thermogenesis in brown adipose tissue.

“Many animals like marmots and polar bears have brown fat, which is there to produce heat.

"When they go into hibernation, they burn this stored fat to produce heat rather than to produce chemical energy.

"So, in some ways snow flies use a combination of the strategies used by polar bears and by Arctic fish.”

Experiments confirmed the antifreeze proteins function like microscopic ice blockers.

By blocking the growth of ice crystals, the proteins stop freezing before it can spread.

In another set of experiments, the team explored whether the snow fly truly could generate its own heat.

To do so, they measured the insect’s internal temperature while lowering the temperature of the surrounding environment to below freezing.

During this cooling process, snow flies consistently stayed slightly warmer than expected - by a couple of degrees Celsius compared to control insects.

Study co-leader Professor Marcus Stensmyr, of Lund University in Sweden, said: “Other insects, like bees and moths, shiver to increase their heat.

“But we found no evidence of shivering.

"Snow flies instead likely produce heat at the cellular level, more similar to how mammals and even some plants generate heat.”

For an animal living at the edge of freezing, he explained that a brief burst of warmth can mean the difference between life and death.

It may give snow flies just enough time to seek cover and avoid freezing when conditions suddenly change.

The researchers also discovered that, in a further defence against freezing conditions, snow flies are far less sensitive to cold-induced pain.

They found that a key sensory protein - one that usually helps animals detect harmful stimuli - is far less sensitive in the snow fly than in other insects.

As a result, it can tolerate higher levels of cold pain, enabling it to continue functioning in conditions that would overwhelm most species.

Gallio added: “It turns out that a specific irritant receptor is 30 times less sensitive in snow flies than in mosquitoes and fruit flies.

“So, they can cope with higher levels of noxious irritants produced by cold exposure.”

The team hope further research will reveal whether other species use similar methods to survive extreme cold.