Bug on wood lid

[Jeir]

I've had something similar in the past, where I didn't put new wooden items in the freezer before placing them in the cage. They liked living in the inside of the house, so I didn't find them until there was a small infestation. It required a full cage clean, and either destruction or freezing of all porous (wood, cardboard) items. Thankfully there was no harm done to my hamster, and I didn't find any bugs in his cage again (or since, with newer hamsters).

Generally, it's recommended to put any new wooden items in the freezer for a couple of days, but I've found 2-3 hours is usually enough. I've never heard about putting wooden items in the oven, probably due to it being a fire risk.