Hi Rob,
I have no idea what flywire is, haven't heard of it before. But I can tell you that they will crawl through the black landscape cloth, and burlap. So they can get VERRRYY skinny.

Thanks jasdip,
Just before I look up landscape cloth and burlap, we call insect screen, for house doors and windows "flywire (or perhaps better)flyscreen.I think that cloth-------- we might call shadecloth which comes in grades of density--- which I'm about to check on now.Thanks for the help.

A good rule of thumb is: if you can see through it, the worms can crawl through it.

In my Worm Factory, I have a layer of plastic screening material followed by a solid piece of fabric between the bottom tray and the catch tray. A few small wandering worms get through the first layer, but not all the way down to the catch tray. They usually find their way back up.