Wingless Midge

Dec 14

Belgica antarctica

The wingless midge — reaching up to 6 mm (0.24 in) in length — is Antarctica's largest permanent land animal. It survives the year-round cold by burrowing, losing up to 70% of its body water, and producing antifreeze-like proteins. Without wings, it sheds less heat and avoids being blown out to sea.

Earth is a planet of insects. There are roughly one million known species — more than half of all animals described by science — and an estimated five million yet to be discovered. The number 10 quintillion (10¹⁸) has been put forth as the total amount of individual insects alive on Earth at any one time. Taken together, that's 70 times the mass of all human beings. These six-legged critters, with segmented bodies and chitinous exoskeletons, are the most abundant life forms known to science, covering landmasses like creeping, crawling carpets. But there is one realm from which the insects are conspicuously absent, or at least, nearly so.

The Worst Place in the World

Clockwise from top left; emperor penguins (*Aptenodytes forsteri*), a brown skua (*Stercorarius antarcticus*), southern elephant seals (*Mirounga leonina*), and a coastline of the Antarctic Peninsula.

Antarctica is the coldest place on Earth; surface temperatures on the East Antarctic Plateau fall to around -98 °C (-144.4 °F). Only the most resilient forms of life, the extremophiles, can survive on this southern continent, having to face glacial temperatures, high UV exposure, shredding winds, lack of food and, perhaps surprisingly, water — for Antarctica is the largest desert on Earth.

Some feathered visitors return yearly to its berg-strewn shores — snowy sheathbills come to scavenge from penguins and seals, brown skuas congregate to breed, and Arctic terns arrive from the very north to experience a second summer — but they all depart again before the onset of austral winter. Adorable fur seals, predatory leopard seals, and behemoth elephant seals have evolved to withstand the coldest of waters around Antarctica, but even they mostly live at sea and seek refuge on warmer isles up north. Regal emperor penguins huddle for warmth and little Adélies chase the scarce winter sunlight, but they don't remain on the Antarctic landmass, instead travelling out onto the ice and into the ocean. Only one animal is known to weather the land of Antarctica year-round, and it is an insect.

The Antarctic Insect

The wingless midge (Belgica antarctica) is the only native insect in Antarctica — of the millions of insect species, not a single other is known to hail from this ice world.

It was first discovered and collected by Romanian naturalist Emil Racoviță aboard the S.Y. Belgica (which gave its name to the midge’s genus), during the Belgian Antarctic Expedition of 1897–1899. The species is found on the rocky coasts of the Antarctic Peninsula and the South Shetland Islands, a jutting of land that reaches towards the southern tip of South America. It doesn't live in the Antarctic interior — nothing does, the conditions are too extreme. Along the coasts and on the peninsula, however, winter temperatures can hover around a "balmy" -12°C (10.4°F), although they can also reach lows of −40 °C (-40°F). The wingless midge, however, cannot survive temperatures below −15 °C (5°F). But it has endured; adapting its behaviour, body, and life cycle to rule the frigid wasteland.

This midge, a black-clad behemoth reaching a staggering length of 6 millimetres (about a quarter of an inch), is the continent's largest terrestrial animal. Its body consists of a long abdomen, three pairs of legs near its head, and two tiny antennae. To survive, it's had to par down its anatomy, simplify itself. Most people will be familiar with midges as annoying insects that fly about and suck blood, but the wingless midge doesn't do either.¹

Each winter, Antarctic winds exceed speeds of 160 km/h (100 mph) — with record speeds of 327km/h (199 mph). These are winds that can rip off roofs and topple trees (if there were any to topple), winds that would abduct a tiny flying insect like a speck of dust in a hurricane, and carry it away to sea and its death. And so the midge of Antarctica lost its wings, both to prevent being blown away and to reduce the loss of precious heat. Instead of taking to the air, for most of its strange life, it shelters under ice.

Life as a Larva

While surface air temperatures can drop as low as −40 °C (-40°F), beneath the snow or ice — even just a few centimetres below the surface — temperatures stabilise and rarely fall below −7 °C (19°F). Here, the midges live out most of their lives; not as dark-armoured bugs but as writhing masses of maggot-like larvae. For two years these tiny worms feed on bacteria, algae, moss, and penguin poop. Through their feasting, they accumulate a build-up of sugars within their bodies, sugars which lower their internal freezing point. Additionally, antifreeze-like proteins run through their blood. And, to top it off, they dehydrate themselves — the less water in the body, the less there is to freeze — becoming partially desiccating by losing up to 70% of their body water (for reference, most animals would perish after a 20% loss). But even so, the midges are essentially frozen for 8 months of the year, only thawing during the "warm" summer months to feed. Their physiology has so adapted to frigid conditions that warmth is now the greater danger. Temperatures of 10°C (50°F) will kill an Antarctic midge in a week, while 30°C (86°F) will roast the midge in a few hours. Thankfully for the midge, Antarctica rarely gets so hot (for now).

Perhaps the one benefit of being the only animal living in Antarctica year-round is a lack of predators. There have been a few observed cases of white-rumped sandpipers plucking up midge larvae, but otherwise, the midge larvae are blessed with predator-free "childhoods" — in exchange for freezing living quarters and a diet of poop. After two years in their wormy larval forms, they finally moult into their adult bodies and, for the first time, venture to the surface. Thousands of these tiny black specks swarm together in a breeding frenzy — a frantic summer orgy — lasting no longer than 10 days, for that is the lifespan of an adult midge. As the final act of a desolate life, the crescendo that two years frozen beneath the snow have led to, the female midge lays her eggs and covers them in a specialized antifreeze jelly — this last gift from their mother becomes the larvae's first meal when they hatch.

Austere Genomes

To survive the Antarctic, the midge has reduced its physiology to the bare essentials — that holds down to its very DNA. At present, the Antarctic midge has the smallest known genome of any insect. With only 99 million base pairs (the A, T, C, and G nucleotides that are the building blocks of DNA) this midge has a sparser genome than any previous record holders, such as the body louse with its 105 million base pairs. The human genome, in contrast, contains 3.1 billion base pairs. This seems an unfair comparison, given the size disparity, but genome size isn't necessarily related to body size or complexity — the house mouse, for example, also has a genome of 3.1 billion base pairs, while the blue whale has only 2.7 billion.

An important point about genomes is that most of them are comprised of "useless code", such as repeated segments of DNA or those that don't code for any proteins. It has been variably estimated that only between 2.6% and 12% of the human genome is actually functional — that is, the sequences which code for proteins that act on the body or regulate the expression of other genes.² Despite being so small, the Antarctic midge genome contains around 13,500 "functional genes" — about the same amount as other flies. It would seem that the midge genome has essentially rid itself of the "clutter" that accumulates in most other genomes, including ours.

Some of those functional genes in the midge's genome are known as aquaporins, which are involved in water transport into and out of cells, and are likely a contributing factor to the midge's abilities of extreme dehydration. Exposed to moisture, it can rejuvenate from a desiccated husk to a living animal once more; the largest on this southern continent, the tiny ruler of Antarctica.

Clockwise from top left; a non-biting midge (*Coelotanypus concinnus*), dung midges (*Scatopse notata*), a biting midge (*Forcipomyia taiwana*), a gall midge larva (*Polystepha pilulae*), and a phantom midge larva (*Chaoborus* spp.).

¹ The name midge applies to several groups of small flies (in the order Diptera). Many resemble mosquitos but are missing a proboscis (the sucking mouth part) — these are the non-biting midges (in the family Chironomidae), but they're also known by a host of other names including harmless midges, blind mosquitos, lake flies and muffleheads. Of these alone, there are some 20,000 species found around the world, including the wingless midge. Although harmless midges don't bite, they do swarm in mass congregations around lakes or ponds, and are wholly unpleasant to accidentally walk through.

There are also the phantom midges, or glass worms (in the family Chaoboridae), named for the transparent, alien-esque larvae. There are "dung midges" (family Scatopsidae) whose larvae live in waste and the adult forms, known as black scavengers, can often be seen swarming flowers. And there are gall midges (family Cecidomyiidae), whose larvae feed on plants and cause bulbous growths called plant galls.

But the midges that so often vex us belong to the family Ceratopogonidae; the biting midges (a.k.a no-see-ums, punkies, and sandflies). As in mosquitos, it is the female midges that bite; requiring the protein-rich blood to produce their eggs. Of these, there are upwards of 6,000 known species.

² The other 80% or so of the genome, the non-functioning parts, were once referred to as “junk DNA,” but more recent studies have shown that many such genes actually do serve a purpose in regulating how other parts of the genome are expressed and possibly affecting the way in which bodies respond to diseases. What this means for the Antarctic midge, and other animals with spartan genomes, is uncertain.

**Where Does It Live?**

⛰️ On rocky shorelines, beneath the snow as a larva for most of its life.
📍 The Antarctic Peninsula and the South Shetland Islands.¹

Size // Tiny
Length // Up to 6 mm (0.24 in)
Weight // N/A
Activity: N/A
Lifestyle: Communal 👥
Lifespan: Larvae develop for at least two years, adults live for only 2 weeks
Diet: Detritivore
Favorite Food: Bacteria, moss, and penguin poop 💩
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Chironomidae
Genus: Belgica
Species: B. antarctica

Most of this midge's life is spent in its larval stage. For two years it is a tiny worm that feeds on bacteria, algae, moss, and penguin poop.

In this larval stage, it accumulates sugars and antifreeze-like proteins in its blood, lowering its internal freezing point. It also loses up to 70% of its body water. Even so, it is essentially frozen for 8 months of the year — reanimating in the warmer months to eat.

This insect doesn't live throughout the whole of Antarctica, just along the rocky coasts of the Antarctic Peninsula and the South Shetland Islands — a bit of jutting land that reaches towards the southern tip of South America.

The temperature throughout the midge's range hovers around a "balmy" -12°C (10.4°F), although it can also reach lows of −40 °C (-40°F). The midge, however, cannot survive temperatures below −15 °C (5°F). So it buries itself beneath the surface of snow, where temperatures rarely fall below −7 °C (19°F).

Heat can be a greater danger to the midge than the cold. Temperatures of 10°C (50°F) will kill an Antarctic midge in a week, while 30°C (86°F) will roast the midge in a few hours.

The midge only lives in its adult form for around 10 days, when thousands emerge all at once in summer and congregate in mass breeding piles. Each female then lays her eggs and covers them in a coating of antifreeze jelly — which the larvae eat when they hatch.

This species was first discovered by a Romanian naturalist during the Belgian Antarctic Expedition of 1897–1899.

Of the roughly one million known species of insects (and many more undiscovered ones) this is the only one that lives year-round in Antarctica. In fact, it's the only animal, period, that stays on the frozen continent for the entire year, making it Antarctica's largest land animal — a whopping 6 mm (0.24 in) long. (Others, like seals and penguins, live predominantly on the Antarctic ice and seek warmer refuge to the north during austral winters).

At present, the Antarctic midge has the smallest known genome of any insect, with only 99 million base pairs (compared to the also small genome of a fruit fly at 132 million base pairs, or a human's 3.1 billion). The smallest known genome of any animal is the plant-parasite nematode Pratylenchus coffeae, which has 18.8 million base pairs.