Straw will work. I'd make sure it's chopped well and mix it with some shredded newspaper. Worms need around 75% moisture and straw isn't particularly good at holding it, the shredded newspaper is and will diversify your bedding.

Here's some thoughts. Don't complete the "bin" until your worms acclimate. Putting new worms into a fresh bin without familiar bedding they will try to escape looking for any hole they can find. I made a complete bin with ventilation holes on the bottom, lid, and around the very top of the sides and after getting a new batch of worms yesterday (and they were pretty small), 8 hours later three quarters had found my ventilation holes at the bottom of my bin and gotten out. The little worm hunter in my house (my cat) was the one that told me there was a problem, I heard her repeatedly attacking the base of my fresh bin extremely excited so I knew there was trouble. I lifted it up and probably 3/4th of my new worms had found the ventilation holes in the bottom and gotten out. So, I did a rescue and fortunately had purchased an extra plastic tote and hadn't drilled holes in it. I moved all the bedding and worms into that tote and put the cover on that has ventilation holes and a bright light on top. Without the ventilation holes in the bottom, they can't escape out there and with the light on up top, they don't want to get out the cover, and with the ventilation they should be able to breathe. I'm going to wait until they settle into the new bedding and get familiar with it before I move them back to the other bin.

Do you plan on always using straw as bedding? As mentioned worms don't like their bedding material changing and try to find the bedding their used to when you add them. If you plan on using mostly straw this time, you have to give it time and do some worm rescues as they get used to straw. Once they acclimate to straw and like it, changing the bedding later to paper repeats the process as they try to go out any holes looking for the straw bedding they're used to and once again you're going through the acclimation process. So, it's better to always use the same bedding material, and if you plan on using straw then stick with it. Another reason I recommend a straw/paper bedding is if you do go to an all paper bedding it shouldn't be a complete shock to them. Maybe a 75% straw, 25% shredded newspaper.

Good luck!

Thanks! Sounds like sage advice. I know a lot of people use paper for bedding; are you worried about the chemicals from the paper ending up in your soil and in the food that grows in it? Also, is there a good way to create the drainage and ventilation holes so that the worms can't crawl out  put screening over them or make them small, for example? I'll be away sometimes for days at a time and would like to know they've stayed put.

Screening is probably not going to work, the worms can fit through extremely small holes. The holes I drilled in the bottom of my bin were smaller than 1/16th and almost all the worms able to fit out it. Baby worms are as small as threads. But, the good news is, once they've adapted to your bedding they usually make it home and don't normally try to find new bedding or try to escape. It usually takes only a few days, a week at most. Then, it's pretty much brainless until 4-6 months later when time to collect the castings! That first hard week as they get used to their environment that's pretty much all the babysitting needed then the worms settle in the bedding, don't try to escape, and honestly go on about business until it's time to move them to new bedding. So, don't worry about anything beyond like the first week and some species seem to have the occasional wanderers regardless. My worm bins have been taken over by my estimates 10,000+ P. excavatus and when I open the bins there always seem to be a half dozen on the sides or crawling on the lid. But, what's 6 worms when there's 10,000+.

I'm not particularly worried about chemicals in the paper. E. fetida is sometimes used to remove toxic minerals/chemicals. They feed them it along with food and somehow in the process the toxicity is neutralized. Once the toxicity brought to safe levels they collect the E. fetida and incinerate them. Why, worms are sometimes used to clean up oil saturated dirt for the same reasons. Paper isn't particularly toxic to begin with, it's the colored ink that had a possibility of containing heavy metals but is mostly non-toxic now, black ink has by law I believe been made of soy based products for years and completely safe. If you're worried, only use newspaper with black ink and no color and you're safe. I feel what, or if colored inks may contain heavy metals, is reduced by the worms in the process anyhow. I don't use shiny paper regardless for a number of reasons, I generally use non-shiny black or colored newspaper, paper from the copy machine/laser printer from work, shredded cereal boxes, and the cores of paper towels & toilet papers I shred and thrown in as bedding. Nothing beats newspaper sent through a non-cross cut shredder in my opinion. Cross cut shredded paper matts and turns into clump balls rather easily, copy & laser printer paper don't absorb water as well nor break down as fast as newspaper. And news paper has the best moisture properties of any paper I've used. If you want to know what the best bedding is, in my experience nothing beats non-cross cutted newspaper.

Straw is ok but make sure there are no seeds that can germinate. The bin can get full of roots.

Marshall

I once soaked a bale of straw, had ground heaped up around it. I seeded it with some worms, got worms clear through it. Once our waste pile of silage in winter was full of worms in the thin layer between the too hot core and the frozen outside. Point being worms will live in just about any organic rich medium under proper moisture conditions.