Hello Hongxi:
I can only tell you what I've observed in my own colonies that are Camponotus pennsylvanicus. I've kept them for many seasons. Your colony sounds to me like a founding colony that's in diapause mode. If this is the first winter rest for this colony, it's best to observe them and make sure they have adequate drinking water and sugar/water. I use small pieces of sponge for this. If they're dormant they won't need much, if any, protein. Monitor them and feed and water them as they require. Don't be fooled by a few ants that don't seem to be part of the winter cluster. I always see a couple of ants that remain active, through the winter rest, they mostly guard and I've seen them bring water back to the nest. Even at room temperature, your ants are genetically programmed to take a winter rest depending on the weather conditions where they've evolved. Ants found in northern areas and mountain regions will take longer rests than those found further south. Your ants will go into diapause and reactivate from diapause when they're ready.
It's hard to diagnose why your friend's ants are in a different phase than yours. It may be that your founding colony reached the proper stage for diapause, but your friend's colony hasn't reached that point yet. I think that once his colonies larvae are at the right stage, his colony will diapause too. Tell me if I'm right. I've often seen my founding colonies rest a month before the larger colonies. Is japonicus the only Camponotus in your area? I sometimes wonder if that might be the reason one of my colonies acts very different than the other two. Maybe they're hurculeanus. Could this be a reason for the difference?
I can only offer suggestions as to what might be happening with your colonies, I hope they help.
RPT
Oh, thank you for the detailed answer 
. *Camponotus japonicus* is very widely distributed in my area, ranging from subtropical to temperate zones. The colony I purchased came from a warmer region around 24.8°N latitude, and I have now brought it to Beijing at 39.9°N (where it has begun to snow, and the rivers have frozen; the local *Camponotus japonicus* are already dormant).
Regardless, I've decided not to disturb them anymore. I've supplemented them with some nutrient solution and moved them to a more suitable location for dormancy (I've observed them rather frequently recently, which might not be ideal for such a small colony). As for the issue with my friend's colony, I'm not too sure either. It's possible that after recently laying eggs, it might enter a phase of low productivity. There are many other *Camponotus* species here as well. Those in the south basically do not enter dormancy, while those in regions with snowfall in the north are highly likely to do so. *Camponotus japonicus* is considered the most widely distributed, common, and relatively large-sized *Camponotus* species in this area.
啊谢谢你细致的解答。日本弓背蚁在我们这边分布的很广泛，从亚热带到温带都有。我购买的群落来自北纬24.8左右的温暖地区，现在被我带到了北纬39.9的北京（此处已经开始下雪，河流结冰，本地的日本弓背蚁已经休眠）。不管怎样，我还是决定不去打扰它们了，给它们补充了一点营养液，放到更合适休眠的位置去（最近一段时间观察的比较频繁，可能对于这个小群落来说不太合适）。关于我朋友的群落问题我也不太清楚，也可能最近产完卵就会进入低产期也说不定呢。这儿还有许多其他弓背蚁，南方的基本上不休眠，北方有降雪的区域大概率还是会休眠的吧。日本弓背蚁算是这边分布最广、最常见、体型较大的一种弓背蚁了
C. japonicus probably does need a hibernation period.
Hi, thanks from your advise
