I found several of these bugs late Sunday night, as I was cleaning up the Monarch larvae. I found 2 literally ON the larvae and 2 on chrysalides. My husband, Steve, and I have killed more than a dozen in the house since. They are small (3-4 mm), black, flying insects.
I reached out to my pollinator friends. Glen Schultz correctly guessed that it was a Pteromalus wasp and she suggested I reach out to Mike Raupp, Professor of Entomology at University of Maryland. Mike confirmed that indeed, this tiny wasp, is a parasite. These wasps are considered beneficial insects. But, they inject their eggs into larvae and, possibly, chrysalides. They don't even need to mate to do this. Holy cow!!!
So, how did they get into my dining room? I had a couple of the containers with me for show and tell at the Marshy Point Fall Festival. They were outside all day. Perhaps they got in then? Otherwise, I'm stumped.
For now, I remain hyper-vigilant, killing every wasp I see. I have separated larvae with "strike" spots (presumably where the wasp injected them). I am keeping my fingers crossed and my prayers going that I may have only lost a few maybe, instead of the whole lot. I would sure hate to see the season go down and end "in flames".