von baumarkthammer » 27. Sep 2013 15:25
In most ant species only the larvae hibernate. So wait until all the brood is in that stadium. Most European species stop hatching and laying eggs when the time is about right for hibernation.
One exaption is the genus Formica, they hibernate completley without brood and start laying eggs in spring again. Also Pheidole pallidula and a few South European species sometimes don't stop laying eggs and require a lowered temperature to get ready for hibernation. So it really depends on which species you keep.