I wanted to come back into the thread briefly, mostly to follow through on the promise that I had made to post any web search hits I found on ball lightning that seemed credible, whether they were positive or negative. To me, the most interesting aspect of this sort of thread isn't trying to judge a shadowy bit of data with absolute rigor; it's more the chance to learn something new - that is, to exercise curiosity about the background subject.
I will say that I don't think conjecture on this thread by the likes of us will ever resolve the video in question. The bug theories still seem to me to fall drastically short; I have already posted one video showing fireflies don't look anything remotely like the moving image in the video; this is what my memories from childhood on tell me about fireflies anyway. But sure, a bug is at least possible. I think we'd all agree ball lightning is unlikely, not least given its extreme rarity to begin with. Other possibilities are something else electrical in nature, whether or not related to the lightning storm, e.g. an arc or other discharge from a power line not visible in the video (although it doesn't look like flashover to me) - more info about power lines and lightning storms
here and
here with a cool video
here; a glitch in the recording; a fake; etc. It would be interesting if the person who recorded the video could be interviewed not only for credibility but his subjective impression of the event. But short of that, there seems too little information in the video for most of us. I wonder if someone extremely conversant with both night-time video
& storm/power grid phenomena (e.g. an actual storm chaser) might be able to make a better guess?
Getting back to the web search I did, I didn't find any claims that ball lightning is merely folklore; it seems to be taken seriously. Below are the better quality hits I found, leaving out some which seemed redundant. They are restricted to relatively recent dates & are either studies or articles based on studies; listed by date going forward. If you just want a quick read that describes the field, the 2012 article by Lowke ("Ball lightning exists . . . but what on Earth is it?") is your ticket - 4th link down.
Toward a theory of ball lightning, J. J. Lowke, M. A. Uman, R. W. Liebermann - 1969 study, Journal of Geophysical Research
On the energy characteristics of ball lightning, A. V. Bychkov, V. L. Bychkov, John Abrahamson - 2002 study, The Royal Society
Birth of ball lightning, J. J. Lowke, D. Smith, K. E. Nelson, R. W. Crompton, A. B. Murphy - 2012 study, Journal of Geophysical Research
Ball lightning exists … but what on Earth is it?, J. J. Lowke - 2012 article on the above 2012 study & also the above 1969 study, The Conversation
Further Insight into the Nature of Ball-Lightning-Like Atmospheric Pressure Plasmoids, David M. Friday, Peter B. Broughton, Tanner A. Lee, Garrett A. Schutz, Jeremiah N. Betz, and C. Michael Lindsay, - 2013 study, J. Phys. Chem.
Observation of the Optical and Spectral Characteristics of Ball Lightning, Jianyong Cen, Ping Yuan, and Simin Xue - 2014 study, Phys. Rev. Letters (this is the study mentioned by
@newjerseyrunner in his comment
#21)
Focus: First Spectrum of Ball Lightning - 2014 article on the above study, Physics (physics.aps.org)
January 17, 2014
Relativistic-microwave theory of ball lightning, H.-C. Wu - 2016 study, Scientific Reports 6