WEBVTT

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Can silk build underwater?. Some caddisfly larvae join gathered materials into protective cases with silk. Caddisflies are insects, and different groups build different silk structures.

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Two material jobs work together. Adhesion attaches silk to a surface. The fiber's mechanical response describes how it deforms under load. Both contribute to a case.

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Build the teaching model. River Shelter gives you six positions and ten silk bonds. Those limits and the material properties are game choices, not biological measurements.

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Current changes the load. For an unchanged piece, this model's load rises with current speed squared. Doubling speed multiplies load by four.

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A design choice has consequences. Turning a twig or leaf reduces its modeled exposure. Extra bonds raise modeled capacity. Neither rule calculates real silk chemistry or survival.

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Compare the same case twice. Keep the design fixed and increase the current. Compare retained pieces and first failure, then explain what the two tests establish.