Hey everyone!
So I have a Formica sub colony going since May in a TH mini hearth. I put them in diapause in my fridge (stays right around 40 pretty consistently) a few months ago. Starting about 4-6 weeks ago, slowly but surely, workers have been coming up to the out word and seem dead or in suspended animation. For the last several weeks it was 6 total but today I noticed there are now 8. There is water in the nestmate and the hydration chamber. I have a byformica feeder filled up top in case they needed it. Back in the fall they seem to want to go into diapause in like late Aug/early September. This is my first ant colony and first time dealing with diapause. Any help y'all could offer would be great, thank you so much!
A few recommendations: Firstly, this is a bit technical, but try to refer to your colony as Formica subsericea, if that is what they are. Other Formica species start with sub, such as Formica subpolita, and probably more in other regions of the world. If you want to abbreviate the spelling the scientifically accurate way, you can refer to them as F. subsericea after using their full name at least once in your post. Just friendly advice!
As for the issue, I would recommend testing the waters first by removing them from the fridge and observing their behavior. My colonies, which are kept at 47 degrees, will start moving around after being out of the fridge for a minute or two. This is a great way to test whether the workers in the outworld are still alive.
If it does appear that they are dead, there are two things I would do. Firstly, raise the temperature of your fridge. In my experience, Formica, especially F. subsericea, tend to nest deep underground in the warm months, and likely deeper underground in the cold months. This is important because the soil temperature is relatively stable the deeper you go. For example, in Virginia, when 2 feet underground, 40 degrees is about the minimum that the temperatures will ever get1. If the ants are dying it could be because the 40-degree temperature you have them at is at the edge of their tolerance, especially for the underfed nanitics. Otherwise, if this is not the issue, the next thing I would question would be the age of the colony. If this colony is in its second winter, these deaths are likely normal, similar to bee die-offs that happen every winter. If this is the colony's first winter though, then multiple nanitics dying off is unusual. I hope this was helpful!
[1] Build It Solar. (n.d.). Earth temperatures and thermal inertia. Retrieved February 14, 2025, from https://www.buildits...emperatures.htm
