Special Liquid Softens Hard Cocoon

a chunky green caterpillar has a red rim around its head where the moth will emerge

Biological Strategy

Puss moth

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Image: Patrick Clement / Wikimedia Commons / CC BY - Creative Commons Attribution alone

Chemically Break Down Organic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Part of the reason that decomposition reactions (chemical breakdown) can occur under such mild conditions is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the breakdown of glucose to pyruvate–and the release of energy–occurs in the 10-step enzyme catalyzed process of glycolysis.

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Modify Material Characteristics

The materials found in living systems are variable, yet often made from the same basic building blocks. For example, all insect exoskeletons consist of a material called chitin. Because material resources are limited, each material within or used by a given living system must frequently serve multiple purposes. Therefore, living systems have strategies to modify materials’ softness, flexibility, and other characteristics. To ensure survival, the benefits of these modifications must outweigh the living system’s energy and material expenditure to generate them. For example, spiders store the liquid components of spider silk in a gland, converting them into silk thread when needed. Some threads have different characteristics, such as elasticity and UV reflectance, than others.

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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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The mouth of puss moth larvae helps them escape their hard cocoon casing by exuding a softening liquid.

“Many adecticous pupae are enclosed in cocoons of varying shape and consistency. That of the puss moth (Cerura vinula) is constructed on the boles of willow and sallow and is of extreme toughness, being fashioned from a mixture of labial silk and bark fragments which hardens into an oval whole, rough and bark-like on the outside but glossily smooth inside. Having no biting jaws, pupae of this type need other means to free themselves from their cocoons. The puss moth exudes a special liquid which softens the casing, allowing the moth to push its way out through a relatively small hole; others have special cocoon-rupturing structures on head or thorax which may be lost on emergence.” (Wootton 1984:91)

Last Updated August 18, 2016

References

Book

Insects of the World

01/01/1970 | Walter Linsenmaier

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