As others have mentioned, more background would be needed to hazard a speculative guess.

Also add small hive beetles (SHB) and predators in general to the list as stress factors others have mentioned.  Even a strong colony may abscond if there are too many SHB.   Predators such as skunks and shrews (if they exist in your area) can stress out, kill or cause a colony to leave.   Same for bald face hornets which can decimate a colony in a matter of hours.   

Forensics will play a big part.  

Examination by an experienced bee keeper of what may look like an empty hive to a new bee keeper might yield some answers.   Are there wads of chewed up bees, is there parts of adult bees scattered about (bald faced hornets), is there cork screwed fecal matter (shrew droppings). Do you see a lot of what looks like mouse droppings, but no evidence of mice in the hive, this is most likely SHB droppings.  Is the comb clean or is there tunneling (SHB).   Do you see webbing and cocoons (wax moth).

Are the honey cells capped or have they been ripped open and have jagged edges... evidence of a weak, dying or dead hive which was robbed out.

An experienced bee keeper will look at any dead brood (capped and uncapped) to see if there is evidence of disease.

Did you witness the colony leaving?  An colony absconding may look like a swarm until you go to check the hive and find it empty.    

If you have a smart phone, the BeeHealth app would be a good app to download and use if you do not already use it.

Steve Petrilli,
Central Illinois

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