Chris mentions:
..."Possibly day length is a  factor that is relevant and, logically, 
this should be more apparent at higher latitudes"...

Race of bee, climatic , forage, colony state and the rest could be 
conditions logical triggers that slow down the laying rate of the queen.

Regarding daylight length - colonies that are in indoor wintering 
sheds/rooms for several months do not have the possibility to see light 
periods. Yet queens do exhibit increased brood rearing towards the end 
of the storage time. Temperatures are controlled (sometimes humidity 
levels  as well). The colonies do come out with 2 or more frames with brood.

Therefore, light periodicity alone is most probably not a factor that 
results in increased/decreased laying rates.

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