Blog Post

Life & Glaciers: The Torrent Midge Lifecycle

(Patagonia’s Untold Stories)

Its skin is splitting open down its back. Three pairs of lateral attachment points keep its streamlined body glued to the submerged rock. It will use the glacial raging torrent to its advantage. With the last air in its body, it inflates its thorax to free itself from its pupal skin. It has violated an unbreakable rule of hydrodynamics. There will be consequences. There is no turning back.

The unforgiving torrent violently rips its fragile soft body away, revealing its nature. It is a female.

The trapped air in her thorax will save her life. Through buoyancy, she reaches the surface and uses her young wings to fly away from the treacherous current.

Torrent Midge adults (Blephariceridae: Edwardsina) from Patagonia Chile. (R. Isaí Madriz)

Resting on an overhanging leaf of the marginal vegetation she completes her transformation by hardening her skin.

Below, others are not so fortunate. Feasting fish engulf the unlucky ones that delayed to surface, while small birds swoop down to snatch those in desperate search for cover.

Mature larvae are under attack, they congregate in the swiftest channels, using the force of the current as their only defense. Their six ventral hydraulic suckers that keep them firmly anchored to the submerged rocks are no match for the jaws of hungry fish.

Adulthood is a developmental stage many will not experience.

Our female braves the predators and flies across the river only to be intercepted by a male. The pair search for cover in the riparian vegetation. After copulation, his life cycle is complete. She on the other hand must stay alive and produce eggs.

Chilean Torrent Midge pupa (Blephariceridae) frontal view. Stacked image of preserved specimen. (R. Isaí Madriz)

A few days pass by and she braves the torrent yet again, but this time to lay her eggs. She selects a large rock in the main river channel and begins to anchor her eggs at the waterline. She must hurry. The unpredictable current thrashes her against the rock face as she struggles to hold on, but persists.

At last, all of her eggs are securely attached to the rock, but she remains in place. Prolonged exposure to the freezing water has dangerously cooled her body. She is unable to take off. The turbulent flow is unforgiving. Unable to hold on any further, she releases her grip and her body is claimed by the very river that witnessed her entire life.

With this action, she culminates a glacial dependent natural cycle that has been developing for millennia, but with the current global environmental threats, for how long will this process be allowed to continue?

R. Isaí Madriz collecting Torrent Midges in Patagonia (Aysén, Chile). (Kristina K. Lindsay Madriz)

R. Isaí Madriz PhD. Photo Credit: Randall Scott/National Geographic

Dr. R. Isaí Madriz is an entomologist and zoologist with expertise in freshwater aquatic insects of Patagonia. As a Fulbright-National Geographic Digital Storytelling Fellow, he is telling the story of deglaciation of the Northern Patagonia Ice Field, focusing on its vanishing aquatic insect diversity through images and stories of exploration, science and human connections. He combines hiking, bikepacking and packrafting to transect unexplored areas and secluded fjords in search of some of the rarest insects on the planet. This low carbon footprint approach utilizes renewable energy sources to capture never before seen footage of remote glacial outlets and hidden valleys of wild Patagonia. Madriz is documenting the largely unknown endemic aquatic insect fauna of this vital region before Chile's Aysén region's biodiversity is transformed forever.

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