are catapillars poisonous to cats?

I know it sounds silly but the kids brought one inside, forgot to set it free before bed and of course the next morning it had vanished. Either it became a kitty snack or is in the dark recesses of my closet waiting to terrify my when i least suspect it. Anyways, my youngest is now concerned that our scrat cat got it. Mind you, scrats health is less then Rosy. His urine is the color of egg yolks (no blood though and tests ruled out all the initial causes) he has a Dr appt tomorrow but the vet is fairly certain it is cancer and our best bet is love and comfort in his final days.
Anyways.. Back to the bug... Are they poisons to cats?

I would think the answer would depend on the type of caterpillar.  Since there are hundreds of different butterflies and moths out there, I'm guessing there are hundreds of caterpillars.  I DO know that there is one particular moth that is poisonous to cats, and that there is at least one caterpillar that can sting pretty bad, but you'd probably know it if he's been stung.   Guess you could call your Vet and ask them if they are aware of any poisonous caterpillars in your area.