nanner wrote:
Does anyone know who the culprit is here?

This took all of 2-1/2 seconds to find on google.

Hosta Pests
Slugs and Snails

Slugs and snails are nocturnal foragers and are the most common pest of
hostas. They eat small round holes in the leaves. By beginning an
abatement program early in the spring, slugs may be easier to control.
Look for silvery slime trails in garden beds to determine if slugs are
present. They may be spotted during daylight hours or in the evening by
using a flashlight. Since some plants are more susceptible to slug
injury, check around those particular plants to detect slugs.
Thin-leafed hostas and those with leaves growing close to the ground are
most susceptible to slug injury.

Chemical slug pellets and baits that contain metaldehyde are widely
available commercially, however label directions must be followed
carefully. A new product came on the market in 2000 that shows some
success in slug control; it contains iron phosphate, which is less toxic
to animals and birds than baits containing metaldehyde.

Beer traps are widely used, albeit only moderately successfully. Place a
small shallow container, such as a jar lid, level with the soil and fill
with beer. Slugs are attracted to it, crawl in, and drown.

Other methods can be used, though they show limited success. Copper
strips sold in garden stores and catalogs may be used to surround
plants. The use of gritty materials such as diatomaceous earth scattered
on the soil surface is also used. Other traps may be made by laying wet
newspapers on the ground overnight. Check beneath these the next day to
find slugs that have taken refuge from heat and sun. Kill the slugs by
dropping them into a 10–20% solution of ammonia and water. Salt will
also kill slugs if applied directly to them.