Here is more on parasitoid wasps, which are distinct from the eusocial wasps that live in colonies. Although their numbers are smaller than their social relatives, there are a bewildering number of species of these wasps, estimated as in excess of half a million.
Charles Darwin found parasitoid wasps deeply disturbing. In 1860, he wrote in a letter, “I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars.” You may find some of the pictures in this video and the article linked above equally disturbing.