they now have two decent sized larvae and 1 egg
What really stounds out to me about this quantity of brood, which I assume has at least somewhat changed/developed since this posting, is that it is actually less brood than my single castaneus queen produced on her own. On a side note, where are things now? Do these queens have nanitcs? Anyways, Even if C. castaneus are truly pleometrotic, which I am skeptical of, I would guess that this kind of behavior is something you have managed to induce in captivity that doesn't happen in the wild. For good reason, obviously. Doesn't make sense to 'cooperate' with other queens if you're gonna end up with a smaller nanitic force anyways.
Do keep us updated on how this goes, though! Curious to see how long these queens last together, etc. etc.
Currently Keeping:
Trachymyrmex septentrionalis
Pheidole pilifera
Forelius sp. (Monogynous, bicolored) "Midwestern Forelius"
Crematogaster cerasi
Pheidole bicarinata
Aphaenogaster rudis
Camponotus chromaiodes
Formica sp. (microgena species)
Nylanderia cf. arenivega