Is it necessary to add worms to raised beds? I built the bed by layering cardboard an newspaper over a piece of lawn before I layered on the soil due to weed problems in my garden. It was a pretty thick layer which I assume will decompose given time but will worms find their way through quickly or should I buy some to supplement in the meantime? Thanks

Lots of info here, let me first say I do raise worms for a living, I dont know everything, but I do know there is tons of miss information out there.
Depending on where you live, as to what type of worm is in your yard, manure pile, field, golf club, keep in mind the same area may have several types in the same location. there is literally thousands of types.
even the "red worm" has many, many different species, depending on who you talk to, as to what kind it is.
when you buy red worms from one person, they will be different from another, all say "red worm" and in fact, to that person, they are........
Worms can be any species and "wild" or "domesticated" some don't domesticate well, so they are not raised as bait or vermiculture.....the worms in your yard-----no mater what kind, are "wild"
the ones you buy online or in a store are domesticated, with the exception of the Canadian night crawler, and those are generally picked from golf course's in cold climates. ever put a wild bird in a cage, or let a domestic bird go. neither will do well.....same with worms. they will, co-exist in raised beds, I add my castings to my beds, and as the eggs hatch it helps them become more "wild" in a sense. If you put some meal or coffee/tea grounds in your beds, and cover that spot with a piece of black plastic, worms will come to it. "wild" worms, no mater what speicise do not breed well in captivity, have been raising and selling worms since 1975........no expert, just some of what I have learn t.....

It is not necessary at all, but it would be best if you did supplement. When I do raised beds I actually dig up the existing soil a bit to incorporate the natural earth early AND supplement for the first season. Worms are not that expensive, and the benefit of having them supplemented greatly supersedes waiting for them to come up.

The worms that you can buy are usually redworms, which you'll find in finished compost or in the mulch layer of a garden. The worms that work the soil, making tunnels and creating good soil structure, are earthworms, which are not generally (ever?) for sale.

So, no, it's not necessary to add worms to raised beds, even if you could find any for sale.

Worms will find their way through the cardboard, no problem. No need to buy worms.

I usually pick up stray worms that end up on the pavement after rain and put them in my pots and raised beds. It's for free and the worms get a new home.