Evolution of Parasitoids

[Jimmyonfire]

Hello Biology dudes, I'm an insomniac and my mind has been wondering a bit. Can anyone explain to me (preferably in laymans terms) how they could have evolved/they and their hosts co-evolved? Parasitoids, that is. It seems so specialised I can't imagine how they got like that.

[Darby]

From a scavenger larva to one that could live inside a living host is not much of a leap; from deposit of eggs on dead or debilitated hosts to lively ones isn't a huge leap. Once you've got a parasite and host, coevolution is pretty much a given.

[Jimmyonfire]

It just sees odd to me that at some point one of the ancestors of a wasp thought 'hmm, yeah, i think i'll lay some eggs inside the head of that moth over there!'. It's just bizzare!

[Darby]

It doesn't become a specific behavior all at once, but there are many instances of adults being influenced to deposit eggs in a spot that matches their own hatching place, which would help a shift in egg placing become set in place over a few generations.