Hi,
If it turns out its not insects, it could be a Rat or a Mouse. I had a Rat chew its way into my home and even chew my antenna cable right to the copper wire in the middle and then it started the chew though the power cable, likely I got to it in time. I first became suspicious when I was up late one night, everyone was asleep so it was quite and I heard noises behind the pantry.
Have a look around for rat droppings. Place some rat baits around and check to see if it’s been eaten. If it is rat or mouse, for now you can plug the hole with steel wool, (rats hate eating though steel wool) till you can get around to doing a permanent job.
Regards from Noelene