People collect bugs in Japan. This isn't the something just for kids-- but in fact adults, with paychecks, buy them in stores or even on Yahoo! Auction.
Look this one here ->
(Here's the auction page if you want to buy it.)
Anyhoo, it appears that sometimes folks also collect bugs to watch them fight. And sometimes they record these fights and post them on the interwubs with pro-wrestling announcements and flying graphics. Like this site: Japanesebugfights.com.
Before you think that this is a free-for-all, apparently there are rules. Three of them. And they are not to be broken. ("Rule 3: No Outside Weapons." !?)
I will freely admit that I couldn't stop watching these videos and that I had the creeps the whole time. That queasy feeling you have in your stomach? It's the bugs.
Here're a couple of the fights. (For some reason, the folks who do this site love fighting with scorpions. I've tried to mix it up a bit.)
Oh! And if you have your own bug fights that you've recorded and want to share with Japan Bug Fights, go for it! There's a submission link on their front page.