Cocoon Lining Prevents Ice Crystals

photograph of orangish-brown and green cocoon inside of a yellow plant

Biological Strategy

Butterflies and moths

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Image: Ian Lindsay / Pixabay / Free non-commercial use

Protect From Ice

Freezing temperatures can be difficult for living systems to manage. They can cause ice crystals to form in blood and tissues, which causes damage to cells and ultimately, death. Living systems can’t afford the energy required to melt ice crystals, so instead, many have strategies to prevent crystals from forming in the first place. Many amphibians, plants, and insects have chemicals that act as antifreeze to prevent icy crystal formation. Another challenge ice presents is that it creates a slick surface, requiring friction to traverse. This is why polar bears’ paws have a rough surface that grips ice.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Oral secretions in the cocoons of many moths prevent formation of ice crystals because they form a fine, dry, web-like lining.

“An oral secretion lining (a spider-like thread) is essential in the cocoons of many moths overwintering in cold conditions: it prevents moisture from intruding and prevents the formations of ice crystals, which would be lethal for the pupa…The cocoon may look rough and chunk-like but the interior surface is smoothly covered by web. This is most important for the cold-hardiness of the pupa. It overwinters in a supercooled state, and if a single ice crystal penetrates the skin, the animal freezes momentarily and dies. The fine and dry web prevents the formation of dangerous ice crystals.” (Pallasmaa 1995:37, 95)

Last Updated September 14, 2016

References

Book

Animal Architecture

22/04/2014 | Ingo Arndt

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