Janet's Cat

Janet Haworth found this beauty in her backyard.
While trying to identify it, I discovered a website that shows lots of promise in identifying caterpillars.  Discover Life displays these larva by color, size, etc.  It didn't show our "cat" but as its database expands, the sorting algorithm may become more valuable.

So, back to Bugguide.com, entering caterpillar and paging through pictures, 50 per page.  This is time consuming, not so much from the search but from all the diversions, reading about all the interesting pictures- weird caterpillars, eggs, and cats crawling with parasitic larva of wasps. A cat on the left (Black-waved Flannel Moth was the only other candidate, but its unruly hair ruled it out.  Finally I hit pay dirt with this link which shows what appears to  be Janet's cat.
Cycnia tenera, (Dogbane tiger-moth or Delicate Cycnia) has a wide range from Canada to the Southern US.  Wikipedia says it feeds on dogbane and Indian hemp as well as milkweed.  Each of these plants produces toxic chemicals which deters many herbivores.  Many caterpillars which eat these plants can store the toxins, making them unpalatable to birds and other insectivores.
Janet's caterpillar develops into a white moth with an interesting talent.  Bats have apparently learned not to eat resting or dead C. tenera moths but will catch them in midair, presumably not having enough time to identify them by sight.  The moths emit clicking sounds when the hunting bats switch from search phase calls to approach phase calls.  When handled by the bat, the moth produces clicks and bats are more likely to drop them than mute moths.  Presumably the coded message is "eat me and you will get sick, sucker."
All this and more comes from this Wikipedia link.