Large Cocoon? - Ask Extension
Hello!
I live in Troutdale, OR and happened to see this cocoon last Sunday as I was chopping old plant stalks down from last year. Unfortunately, I...
Knowledgebase
Large Cocoon? #926877
Asked March 27, 2026, 2:57 AM EDT
Hello!
I live in Troutdale, OR and happened to see this cocoon last Sunday as I was chopping old plant stalks down from last year. Unfortunately, I had already cut the stalk that this guy was attached to. I quickly relocated it to my trumpet vine in a safe spot. I am very curious about what could be growing in the cocoon and would be so appreciative for any info!
Pics attached.
Kindly,
Melissa from Troutdale
Multnomah County Oregon
Expert Response
Hi Melissa,
That is an egg case (ootheca) of a praying mantis. Here is a link to a photo of another one for comparison....
https://www.bugguide.net/node/view/1645693
In our region, that mantis egg case is most likely to be from an introduced European praying mantis, Mantis religiosa. We do also have some native ground mantids (Litaneutria species) here, but they are smaller and much less common.
European praying mantis egg cases generally contain about 100 eggs. The egg cases are laid in the fall and the baby mantises hatch out in the spring.
Hope that helps!
That is an egg case (ootheca) of a praying mantis. Here is a link to a photo of another one for comparison....
https://www.bugguide.net/node/view/1645693
In our region, that mantis egg case is most likely to be from an introduced European praying mantis, Mantis religiosa. We do also have some native ground mantids (Litaneutria species) here, but they are smaller and much less common.
European praying mantis egg cases generally contain about 100 eggs. The egg cases are laid in the fall and the baby mantises hatch out in the spring.
Hope that helps!
