How did parasitoid wasps evolve their life cycle?
This is similar to the seahorse problem, in that it requires a distinctly non-mammalian perspective. Parasitoid Wasps, Natural Enemies of Insects provides a more in-depth explanation.

Existing wasp strategies may illustrate the possible transitional forms. It is not a linear transition: all of these have branched off and there are multiple parasitic strategies.


Solitary wasp, captures prey to feed to its larvae
Ectoparasitoid wasp, which lays its egg directly on prey that is paralyzed or otherwise unable to resist as the larvae eats it alive
Endoparasitoid wasp, which has formed a symbiotic relationship with a virus that disables the prey's immune system thus allowing eggs to be laid inside the prey
Hyperparasitoid wasp, which preys on other parasitoid wasps