After catching it, I put it into the refrigerator; the next day, as I released it outside, it was briefly numb enough for me to get a few pictures before it flew away.
Only today I was talking to my neighbor Bill who grew up in rural Pennsylvania. I had mentioned hellbenders; that led to water dogs eventually, but in the meantime we passed hellgrammites. He remembers hellgrammites (the larvae of the dobson fly) from his boyhood fishing days.
Gardeners take note: don't confuse Corydalus with Corydalis.