but be carefull!..worms also like cepes..
when buing frozen ones try to buy only whole ones and the smaller the better. less cahnce of 'protein' inside.
cepes just putting into saltwater and hope the wigglies will float to the top (like i nsaldand veggies) does not always help. the worms are deep inside the mushroom so to be on the safe side, just cut them in half...and have a look.
never buy 'sliced' they contain most of the time just the heads and even more time they are brown, mushy and full of holes.
you are right, if you are not 100% sure what it is, don't pick it yourself. and for a restaurant i never would use something that does not come from a commercial company / firm /supplier. risks nowadays are just to big.
good food, one of the few pleasures left to mankind...