So I was checking up on some of my ants. And I noticed that one of the pupae looked very strange. I turned the tube around to get a better look and realized the pupae's head was completely gone. Like, completely torn off the body. The workers weren't tending to it anymore and completely ignored it, confirming that it is dead. I couldn't find the head anywhere. And the other pupae were fine.
So my question is, why? I assume the ants killed it, unless there's some other explanation. Were the ants stressed? They had more than enough protein, and water. Is there a way I can prevent this in the future? I'm just really confused because I've never seen that happen before.