|MadSci Network: General Biology|
Insects have tiny pores (one to several microns wide) in their eggshells that allow atmospheric oxygen to cross into the inside of the egg. These are called aeropyles. I assume (although I have not found much in the way of literature on the subject in my short search) that spider eggs are similar. In other words terrestrial arthropod eggs are permeable to oxygen. Reference: Hinton, H. E. 1970. Insect Eggshells. Scientific American.
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