Old fashioned good housekeeping...........hoover it *every* day, brush it out and keep it clean and dry.
What are the wooden walls covered with ? If it's varnish, wash them down with a well wrung out cloth that's been washed out in a bucket with washing soda, a small squirt of Fairy liquid or the like and a couple of drops of orange, pine or lavender oil. Buff it dry to a shine.
If the wood is untreated then you need to wash it down with soap and water and dry them thoroughly then use a furniture polish on the boards. The usual mix is turpentine, beeswax, a little soft soap and some essential oil.
The oils actually help discourage insects and insect attack as well as freshening the whole room.
If the walls are papered..........well it depends on the paper. If it's cheap sugar paper type stuff so long as it's sound you can brush it thoroughly (it'll be covered in mini bits of paper and the woodlice enjoy them with the starchy paste) and hoover frequently.
If your landlord will allow you to paint it then the smell of the paint will also help discourage the insects.......and it ought to allow for you to caulk (decorator's filler) the gaps too beforehand.
As you clear up one bit keep working outwards, otherwise the insects will just recolonise from elsewhere.
If you have such a problem with insects it's possible you might end up with mice too as the nights draw in. Keep it clean, all food securely stored and there's nothing for them to eat. You really want to discourage nesting if you can. They really don't like being disturbed.
Ten minutes a day with a hoover is worth the effort of keeping on top of the problem.
Atb,
M