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Nature Notebook – Praying mantid egg cases

Keen observers walking through a sunny field can spot the egg cases (oothecae) left by praying mantids on tall plant stalks. If they touch the foamy-looking mass, they will discover that the material is quite hard.

The females lay their tiny eggs on the stalk. Using special glands in their abdomens, the females produce a form of silk to cover the eggs. It emerges from the abdomen as a foamy mass that hardens over three to five days into a protective hard cover. Each ootheca can contain up to several hundred eggs.

Biotechnology scientists have been studying the structural features of oothecae. The fibrous protein (silk) folds into coiled coils (like the famous DNA helix). Scientists are hoping to use that form as a template to “build” other structures that are as sturdy as the mantid oothecae.