I found the exact same thing. Have it in a butterfly containment to see if something hatches. It is in a dead papaya leaf, shape is a hollow cylinder.

Thanks for the insights and picture. I'll keep a watch on my cocoons and hope that something emerges.

I agree with both comments, and I think it's safe to say these are cocoons of braconid wasps specifically.

... it's difficult to tell based on this photo. There may be other insects that produce similar egg masses. Many members of Lymantriidae lay eggs in a frothy substance. The hollow core that you mention, however, suggests that the mass surrounded a caterpillar (no longer present) that was parasitized by the eggs of wasp or fly which, when they emerged from the host caterpillar created a "group cocoon" surrounding the moth larva. The photo shown below is © Molly Robertson and appears on a Page at Moth Photographers Group. The photo, taken in Puerto Rico, shows a caterpillar of a Sphinx Moth, Erinnyis ello.

You may have hit the nail on the head with "cocoons". They look like they might be cocoons of small parasitoid wasps. If anything hatches out, definitely post photos!