When I think of the predators of caterpillars, I think of birds and lizards. But a more common killer is the Braconid wasp. These tiny wasps find soft-bodied caterpillars including cabbage worms and hornworms and firmly attach eggs to them. The developing wasp larvae live off the caterpillar without killing it until it develops into a chrysalis. At that point the wasp larvae mature and burst out of the chrysalis, killing the developing butterfly or moth. The wasps then go looking for more caterpillars. Thus the life cycle of the butterfly is stopped.
The wasps have been used to control hornworms, where they prove a partial solution. It’s imperfect because the wasp larvae allow the hormworms to continue to feed. Further infestations, however, are blocked.
The wasps are used on farms and in gardens. The emergent small wasps don’t sting unless molested.