It could have been to do with the "protective layer of mist" which was covering the chamber which the eggs were in. It may have been able to provide a normal atmosphere, capable of housing living organisms without them being effected by the vacuum of space. It's just a guess though, as I honestly am not quite sure what the layer of mist was used for, & the eggs were deep in the bowels of the ship, so it may have been used to ensure the safety of the cargo in the event of a hull breach. By the same principal, it could have kept whatever other small animals which had found their way into the chamber, such as the insects, alive & sustained.