I have observed something similar to Runner12's experience in my Camponotus novaeboracensis colony (about 40 workers); the larvae had stopped growing and the queen was no longer laying eggs. I asked around, and SYUTEO said, "I think I heard somewhere that says Camponotus need urea in their diet to produce certain amino acids. It has been theorized that some colonies die mysteriously due to lack of urea." And according to SolenopsisKeeper, fruit flies contain urea. After I started feeding them fruit flies, the larvae all started to grow and are now about to pupate. The queen is also laying eggs again.
Perhaps this proves that theory; however, I did feed them the fruit flies alive, whereas I fed them other insects dead. Maybe having to catch their prey encourages them to eat it, or could fruit flies really contain a nutrient that is essential to their growth?
I had the most explosive growth with fruit flies. Fruit flies were alive as well; mine don't seem to enjoy dead insects nearly as much. They hunt effectively.
