It apparently isn't just the deer (or rabbits; I never figured out which, but I'd put money on the deer) who have developed a taste for my cattails. Luckily, I had started to move some out of the Puddle in anticipation of eventually cleaning the pond for the first time in many years (and perhaps rescuing at least part of the filtration system now hopelessly tangled in cattail roots) before most of the remaining plants were neatly and cleanly chomped off.
Nary a leaf tip was to be found, which is why I'm blaming the deer. One three foot long leaf would have made quite a belly full for a cottontail; even a dozen such--which is pretty much what disappeared--would barely appease the hunger of one of the hoofed grazers.
A sprinkle of frass (fancy word for caterpillar poo) across the surface of the water where the relocated--to the large deck--plants are now residing hinted that something else was munching away on the cattails, as well.
Took a bit of searching to find this beauty, for obvious reasons. (Then the camera obviously refused to cooperate with a highly cooperative beastie. Argh.)
Grab favorite caterpillar book, cross-reference "cattail" and… It's not referenced as a food plant. Hundreds of other plants are, but not cattail. Nor common reed. Nor phragmites. That's the limit of my knowledge of grass-like vegetation. Hmph! My favorite caterpillar book has failed me. What's with "highly variable" caterpillars within one species, anyway? And why show a photo of the most "plainly marked variation" of the most likely candidate? Double Argh.
I'm making an uneducated but intuitive guess and will say some species of cutworm... (Correct ID welcome!)