Waterproof

... distribution system, the tracheal system, although some do carry oxygen in the hemolymph, using a variety of carriers. Insects are too large (and waterproof) and have metabolisms that are much too high for simple diffusion to work for them.

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The membrane and the cuticle are different things, the cuticle is a waterproof layer, very little watter goes out that way.

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... epidermis. The outermost layer of cells of the epidermis contains keratin. The keratin in these cells makes the skin tough and almost completely waterproof. In places where the skin is exposed to much rubbing and pressure – such as parts of the hands and feet – the number of cells containing ...

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... the outer layer of skin cells is usually dead anyway I believe. There is also a substance that is secreted, keratin I think?, that makes our skin waterproof. Overproduction of this makes the skin not stick to itself and causes dandruff.

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