i identified it! a hackberry butterfly
I sent this picture yesterday, today I found a great book Butterflies and Moths of Missouri and I found my little butterfly. It’s a Hackberry Butterfly.
We are very happy your letter does not contain a chilling account where this exaggeratedly large and aggressive creature terrorized your children (love the photo), so you squashed it. We also appologize for not answering your letter yesterday, but our mail volume is very high. We did locate a nice webpage with the stages of metamorphosis of the Hackberry Butterfly, Asterocampa celtis celtis. This past spring, Thomas from Madison Wisconsin also sent us complete photos of the Hackberry Emperor metamorphosis.