|Photo by Ned Harris 5/23/2014
Mantis egg casings (like this one) often have tiny exit holes. (They aren't from the mantises hatching, though.) Soon after the female mantis extrudes her eggs and the foamy goo that hardens into the egg casing, a parasitic wasp female lays her eggs in the goo. The wasp's eggs hatch first, the hatched wasp-lings eat some (but not all) of the mantis eggs (and such), then eat their way out of the egg casing. (Don't try this at home.)
Great molting mantis photos from our favorite bug lady, Margarethe Brummermann.