Found on the stem of a (non-native) hydrangea in very early spring. Recognized as Chinese mantis before deciding to cut ootheca open. Very interested to see cross-sections inside. Many deep freezes this winter (e.g., down to 6 degrees F several times), and young obviously not alive inside. (Pictures get a little gruesome toward the end.)
Ootheca could easily be rotated 360 degrees around stem.
Large black butterfly with yellow spots on tails, yellow bar across the forewings with yellow on hindwings.