A study of insect embryos' waterproof membrane, the serosa, reveals that the membrane is crucial to the process of preventing eggs from drying out or absorbing too much water. The experiments involved blocking the serosa production gene in red flour beetles and found that only 6% of the eggs hatched in a dry environment; in extremely humid environments, embryos failed to develop at all. The serosa may have evolved to allow ancient insects to lay eggs on land, rather than having to rely on water, speculates Chris Jacobs, one author of the study.

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