[Reallymary]

Installed Nuc June 17, into 10-frame deep, 4 frames bees and brood, 1 feeder and 4 empty frames, (they were pretty lively so got intimidated and shut hive without putting in last empty frame. ) Inspected June 19, added feed, no issues.
Inspected June 23, holy cow they were mean, plus they had built two gorgeous really big combs ( in 4 days!)off the top of hive hanging all the way down down in empty space where missing frame should have been. But it’s hooked on to the cover, I don’t want to lose it ,, but do not know what to do next. They were so aggressive I didn’t dare examine any other frames (I was suited & using smoke)Managed to add feed and close hive.
My questions are:
Can I save hanging comb?
What the heck is with these mad bees?
I’ve handled bees for 4 years and have never encountered a hive this bent on destruction of me.

 

[Ravenseye]

Let's start with the comb. Yes, it can be saved. Pick a cooler day where high temps won't make the newly drawn comb very "rubbery". Gently take the cover off by pulling straight up. Place the cover over two empty boxes turned on their ends or a couple of saw horsed...something like that so that you can get to the comb out in the open. Take an EMPTY frame (I use wood but if you use plastic you can cut the middle out of the frame leaving a nice big hole to work with). Hold the frame up to the comb that the bees built and estimate what will fit. Brush off or smoke out the bees as best you can from the comb and then cut it out and off of the cover. Install it with rubber bands or wire onto the empty frame you have which then gets installed back into the hive. While you're fitting it in the frame, don't use the top of an outer cover from an adjoining hive if it's been sitting in the sun. You can imagine how I know about this....!

As far as the cranky bees, check to make sure they are not queenless. That said, I've often had real mean bees for a few days after moving them from a nuc into a hive. Not sure why. They usually (but not always) settle down after a bit.

Finally, if they are real mean, just leave them alone. Forget about the comb. This time of year (not sure where you are though....you should add your location to your profile), a strong nuc can quickly fill stores and produce brood so if you have to give up on that comb don't sweat it much.