Do you have holes in the lid of your bin... for "airflow"? Doing so also introduces a minimal amount of light into the top of the bin at all times, which helps keep them "buried". You can also leave the lid totally off if necessary (which I've done to have the light keep them at bay despite bin conditions) as long as you keep check on the moisture content and the smell is not atrocious. ;)

I've attached a pic of mine. No holes in the side... just (many) drain holes in the bottom on the lowest spots and the lid.

My large worm bin is a commercial one given by the city at their workshop, and it has 2 air holes at either end. That's it, no other holes. The lid snaps closed, tight.

My other bins are buckets that the likes of Dairy Queen, Williams Coffee Pub throw out, that muffin mix, whipped cream etc come in. No holes in them at all, so the lids are ajar or completely off.

I haven't had any escapees or crawling on the sides, maybe a couple or so worms exploring once in a while.

Having said that, I worry if people new to worming, keep their lids off to force them into their bedding. If there are a large number of worms escaping or trying to escape, there's something wrong, and they're not happy. Forcing them into undesirable conditions isn't fair.

"which I've done to have the light keep them at bay despite bin conditions"

That sounds mean to me.

Im afraid Im at least one of the people to suggest leaving the lid cracked an inch or less. Im glad to hear you say that helped your situation. I guess I also pamper my worms a little too much. I even used a spade bit drilled windows and hot glued some fiberglass cloth up. I also cut out the bottoms and put hardware cloth in the bottoms- I also put wood strips to prop up the bins for a little more air flow. I wouldnt expect anyone to do what I do just sayin.

I had small holes (3/16 inch?) drilled every inch around the perimeter of the bin (Rubbbermaid tote) just under the rim at the top. The worms seemed to be fine with that.

I may borrow the drill again and add the holes just under the rim around the top edge - I like that idea. The ones I drilled on the lid look just like dzignr's, only more spread out and totally not in perfect lines! But about the same size and number.

Hummersteve, love the screened in windows. Your worms are definitely living the life of luxury - if mine found out, I'm sure they'd be envious!

Jasdip, I agree that chasing them back underground with light is not ideal, but I think it's better than letting them wander too far and drying up on my floor before I can return them to safety. Fortunately, that hasn't been necessary since the improved airflow strategy.

I dont have any holes in my lid I dont feel its needed, although its fine to have them. Once you get your bin squared away the worms wont leave at all.

I drilled a MONSTER amount of 1/16" holes on all sides and the lid AND the bottom. The only time worms seem to want out no matter WHAT is during a bad thunderstorm. We have a monsoon season here in No. AZ but with a light right over the bins they seem to stay in the bin. They WILL however "ride the sides" enmasse during these storms. IMHO they seem to "know" that a heavy rain will drown them so they seek higher ground. It seems that the survival instinct outweighs the fear of light.

I have a RM bin (ca. 14 gal.?), NO DRILLED holes anywhere and is running in the 4th year. I cut out most of the lid, leaving a lip of about 3/4". Roughen that 3/4" with sandpaper and attached weed cloth with contact cement to cover the hole. It has worked for me so far.

Otis, what a great idea! I'm prevented from adopting that one because of visions of my cats jumping up on the lid and going straight through.

I scored some corrugated cardboard today at work that is nearly an inch thick. I was pretty excited, and this is pretty much the only place I can celebrate that victory with any hope of being understood! I already chopped a few pieces off and threw them in, just for fun.

Joyousfree: My problem was with raccoons. One morning there were 2 big rips in the weedcloth. Rather than replacing the entire cloth, I patched it, practicing my sewing, lol. I found 2 pieces of wood (2x2") with a length a bit longer than the width of the lid, put another (whole) lid (or a solid cardboard if it's inside) on top and something heavy on top of that to keep it in place. No more mishap since.
Not as much airflow as without the additional cover but I found it better than drilling and limited access for flies.

@jasdip: I agree with joy,,, better than having them crawl out and dry up. It was also during my first week of my first bin and I'd added some bread that heated up a little and was apparently making some go AWOL. I discovered a couple were making a run for it as I was going to bed at 11:00 pm and turned on the light overnight to avoid a mass escape until I could figure out what the deal was the next morning. Bottom line... it worked.

Christ... you'd think you were going to report me to ASPCA for pet worm cruelty or something! :/