Hi, I’m a newbie! On May 20, 2018, the Bee’s in one of my hives all vacated the hive for 10 minuets just flew around near the hive, then the bee’s calmed down and returned to the hive. I really was a sight to see, thousands of bee’s.
I did an inspection after this “swarm” and everything seemed to be normal.
Any idea what caused them to leave the hive and then return?
Thanks,
Dan
Did you shake bees off the frames? Are you sure that there are no queen cells? Sounds like a practice swarm, which means they will probably do a real one in the next week or less. 
I did the inspection after they swarmed from the hive. This hive is only a month old. Received a Nuc end April.
After the bee’s calmed down, I did my inspection. I saw no queen cells - Hive is new, about 2 months old.
I still need to know whether you saw queen cells in the brood box. Do you have an 8 frame or 10 frame brood box? How full is it? Do you have any photos? It is very hard to help you without knowing what you have seen inside the hive. I want to help you, and I am sure many others on this Forum will too, but we just don’t have enough to go on at this point. 
If you don’t know what queen cells look like, here is a nice leaflet:
http://www.wbka.com/wp-content/uploads/2015/04/wbka-booklet-english-PDF.pdf
Edit - my message posted seconds after your follow-up :-
Ah OK, if there really are no queen cells, then the behavior is very difficult to understand. Nurse bees are extremely good at hiding queen cells, so unless you shake them off each frame (or smoke them back and forth), you will find it very hard to be sure that there were none.
How full was the brood box?
Thanks, but I saw no queen cells. I have a 10 frame brood box, 6 out of 10 frames are almost full.
The bee’s are busy bringing in pollen. As I said this is a new hive, 2 months old.
I did use my smoker but very limited as I did not want to agitate them further. Yesterday our weather warmed up quickly, we have been having rain for the last week (East coast -NJ) here. The temp. reached mid 80’s and was very humid. Typical NJ Summer weather. I thought maybe the bee’s got HOT in the hive…
When they get hot, they don’t usually fly, they “beard” on the outside, usually on the shaded side or the front. I will be very interested to hear what happens over the next couple of weeks, please update us if you have time. Thank you! 
I will keep you posted, Thank you very much for the response!
Dan
Sure sounds strange. Still, if you shook all the frames clear of bees then they aren’t preparing to swarm. Is your queen clipped?
Hi Dee, We have had a weeks worth of rain here in NJ. 5/20/18 was a beautiful sunny day, the temp. rose quickly. I bee’s left the hive for approx. 10 minuets before they returned, that’s when I did my inspection.
No, queen is not clipped.
Today 5/21, the hive looks/sounds normal, bees are busy forging.
Bee’s returned to hive after about 10 mins.
After a lot of rain, you’ll often see a lot of bees doing orientation flights, which can look like the bees are swarming, usually early in the afternoon. It may have been too wet for any orientation flights during the rain, therefore there will be a greater number of bees doing orientation flights all on the one day. That’s my theory.
It’s definitely been a long stretch of rain in these parts. But, I believe I saw my bees doing a practice swarm yesterday, now that I’ve read this post - thanks @Dee! I caught sight of the air above my back yard just filled with a bee vortex, it was like nothing I’ve seen so far. Definitely not mass orienting, even though that’s a quite feasible thing after bad weather.
Anyway, they seemed to disperse, or move off out of view, and I assumed they clustered elsewhere and I’d missed them. But, today while I was at work, my husband texted me that they were doing their wild vortex again, and a little later sent a pic of a huge cluster hanging up high in a holly tree just behind the hives.
The branch was up about 20 feet, but luckily my hub is an arborist 
He and our son got two ladders & two pole clippers, son pinch anchored one end of the branch and held it while dad sawed the other end. Bees were rather disturbed but the cluster was fairly intact – until it got bumped on the way down 
The branch still had bees on it, but clearly the queen was not among them because in a few mins they had flown back, all the back up to where they were. The guys did the same procedure again…and then lost grip and the cluster came all apart, vortex in the air, then amazingly they began flying back to their hive and marching back in!
So my son and I did a split. Hopefully we did it right, and I have a new colony and no imminent swarm in the old. No time to sit back though, because the other colony looks like it’s getting ready and I ran out of time to inspect today! The rain for past week plus really has me behind in all outdoor pursuits 
Good work @Eva
Long bouts of rain are a real pain. The bees have nothing to do but plot queen cells and the minute the weather breaks they are off!
See it a lot here and you have to be on your toes.
Thanks, Dee, I hope so. Am awake now worrying that I took queen cells along with the queen into the new split…my son and I couldn’t spot her after three or four thorough looks over each frame, so we took what seemed the most likely frames out. Never shook bees off - and boy they were layers deep - so I guess I just can’t be sure if some QCs went along.
Thought I’d look in on this in a couple days, what are your thoughts about that and what might be done depending on what I find?
Gosh that sounds like a lot to ask in one question 
I appreciate any advice!
If you have had a spell of rain bees will still hatch but they can not fly in the rain so when the rain stops there will be what could be seen as a swarm but the bees are in fact doing orientation flights. If there is no queen cells then they are not swarming. Add a honey Super when the hive is 80% full of honey, pollen and brood. I prefer frames with wax foundation.
Regards
An interesting read Eva and you going into mid Spring swarming is something to look out for, glad the boys didn’t have to trim the whole tree!!!
Thanks Peter, I was able to see two fully formed and capped queen cells along the bottom of one frame, and also one on the top of a frame, open at the top & containing a fat larva that several bees were attending to. It must have been torn open when I removed the upper brood box…later on, when we had exhausted ourselves looking for the queen and just decided to go with our best guess (the two frames closest to the entrance, that were layers deep in festooning/clustering bees) I wanted to make sure and leave the frame with the big queen cells in the mother hive. It’s fuzzy now with all the hustle bustle we got into, but I do think I did so…a marker in my pocket would’ve come in handy!
I am working through my hives and marking the queens but they can do a good disappearing act. In my hive inspection I just look for brood to know the hive is queen right but being able to find her is a bonus.
I am thinking of a voice operated voice recorder so I can play it back later to put what I have done on my computer - I can’t rely on my short term memory, which is sometimes a good thing!!!
Regards