The Antarctic Midge (Belgica antarctica)

Dear Readers, if I was to ask you to guess the largest purely terrestrial organism native to Antarctica you might, like me, scratch your head a bit. Seals aren’t purely terrestrial and neither are penguins. But I would never have guessed that the answer would be a 6mm long midge, named ‘Belgica’  after a Belgian expedition from 1899. The naturalist onboard collected a specimen of this midge, unknown to science previously. But how on earth does it survive in such a cold and barren place?

First up, this midge is flightless – the winds in Antarctica are legendary, and you wouldn’t want to be a tiny insect blown into the water or onto some even more hostile plain. In fact, the Antarctic Midge can only survive temperatures of -15 degrees Celsius, while the Antarctic regularly drops to -40 degrees. Rather the face the extremes of the weather, the midge burrows under the snow, where the temperature rarely drops below a ‘mere’ -7 degrees.

Even at these temperatures, though, the Antarctic Midge requires a bit of antifreeze – its tissues contain glucose, trehalose and erythritol, all forms of sugar that prevent ice crystals from forming, and help to stabilise the proteins and fats that the insect needs to metabolise.

In fact, the Antarctic Midge is so well adapted to freezing temperatures that exposing the larvae to temperatures as low as 10 degrees Celsius will kill them within a week. However, they can survive losing up to 70 percent of their bodily fluids – larvae born on the west coast of Antarctica live without water for the whole of their larval cycle. They reduce water loss by clustering together, and by doubling the concentration of sugars in their bodies, which helps to thicken their ‘blood’ and makes it more difficult to lose fluids.

Antarctic Midge on Moss (Photo By Igor Gvozdovskyy – Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=97127382)

For such a little creature, the Antarctic Midge has a long life cycle – it can take four years from egg to adult, with two long, cold Antarctic winters spent as a larva, dormant under the snow. During the larval stage, the young midges will eat moss, detritus, fungi and micro-organisms. The timing of the final emergence as adults is crucial – the adult midges will only live for ten days, so they have to find a mate and lay their eggs in this short time. The males emerge first and perform a mating ‘dance’ (similar to that of the Winter Gnats that we heard about a few days ago). The males can mate multiple times, but the females lay only one batch of eggs, after which their reproductive tracts are damaged and they are unable to produce any more. The females cover their eggs in a blanket of jelly which acts both to protect them from freezing and keeps them from dehydrating – this will also provide the first meal for the larvae when they hatch.

I wondered what on earth the female midges fed on, and the answer is ‘nothing at all’ – neither sex feeds after it emerges as an adult. What would they feed on, after all? The penguins are largely not around in the summer, and any animal that they fed on would only have to jump into the water to get rid of their irritating little friend.  The Antarctic Midge is  decidedly preferable (from a human point of view) to the fearsome Scottish Midge, where the females need a blood meal in order to provision their eggs, and they aren’t at all fussy about where they get it (although if I’m in the vicinity they show a distinct preference for me).

What an extraordinary animal the Antarctic Midge is! A survivor and a specialist. Let’s keep our fingers crossed that the Antarctic continues to be cold enough for it to survive, because if it’s too hot for the midge, the consequences for all of us could be pretty dire.