I also think that they must be eggs, I've just posted a picture with some, see here. Hence your larvae must be first instars, freshly hatched probably.

Lovely hairs on the larva's body. Excellent picture. Mine were taken not too far away though.

Thanks! Good to see my hunch was correct!

It was interesting to see that both our finds were at the same developmental stage.
The eggs are huge, aren't they? This raises several questions, mainly how big are they inside the female?
I've read in The evolution of social behavior in Passalidae, Jack C. Schuster and Laura B. Schuster, in The Evolution of Social Behaviour in Insects and Arachnids that they produce 2 to 4, rarely 6, eggs per day, and nests usually have fewer than 35 eggs. Now this is a lot, don't you think?
It would be interesting if someone dissected a female early in the Spring, just an idea... Alas I can't do it myself.