This is a very dead caterpillar. The poor thing had been parasitized by a Braconid wasp. The eggs laid on the caterpillar eventually hatched, the larvae grew, pupated on the body and emerged...you can see the round holes on this shell or husk of the caterpillar. The wasps that cause this are called "mummy wasps" because the caterpillar host becomes stuck to a plant and mummifies, a process that is not pleasant! The round exit holes are characteristic.