Mantis Ootheca

Subject: Hard Shell Mystery
Location: Silver Lake (Los Angeles)
May 24, 2015 4:39 pm
Hi Daniel
A neighbor noticed this disturbingly large hard shelled , something on my fence this afternoon. About 2 1/2″ long, 3/4″ wide , 1/3″ deep. A pupae perhaps? The neighbor poked w/ a stick & it fell off (although it was stuck to the fence quite well), and we lost it in the leaf matter. There’s something very prehistoric about it. Never seen anything like it before.
Signature: Diane E

Hi Diane,
This is the Ootheca or Egg Case of a Mantis, and we believe it might be that of a native California Mantis based on these images on BugGuide.  It looks to us like the Ootheca has hatched, likely releasing several hundred tiny Mantids.