If you said: "Mantis Egg Casing" - you win! See this post for photos of the nymphs coming out of the egg casing. And this for more on Mantises.
|Photo by Gene Spesard 1/29/2014|
The holes here are not from the mantis nymphs, but rather from the larvae of an opportunistic wasp. The female mantis lays her eggs in the froth she extrudes at the same time; the female wasp lays her eggs in the mantis' egg casing before it hardens. *Yes, the wasp larvae do eat some of the mantis eggs, but not all of them. So don't worry if you see holes in the egg casing. There are likely still plenty of mantises to go around.
*Correction from Fred: (even weirder than I imagined!)
The wasp larvae (grubs) actually continue to eat mantis eggs until they pupate within the egg case and are protected. When the adult wasp emerges from the pupa, it then chews its way out of the egg case making the exit holes.