I've been battling an unknown bug now for 6 weeks (from mid December). I am disposing of around 5 a day from my bathroom and the adjoining room. I live in a downstairs flat in South Tyneside. I can't see where they are coming from but presume its either from behind the bath panel or wall cavities/skirting boards. I have so far used a full tin of expanding foam and I am on my second tube of silicon in a bid to seal every possible place they are coming from, but every day they still appear!
The picture with the edge of the toothpaste tube in shows scale (the black section of the toothpaste tube is 4mm). They seem to move very slowly when watched but will appear out of nowhere when I check for them. I think they have wings as I could have sworn one tried to fly when I went to remove it. I am presuming they are a beetle but really I have no idea?
This may or may not be of any help but this is a weevil, beyond that though hopefully someone else will be able to help more,
Can't be absolutely sure from these images but could be the New Zealand immigrant Euophryum confine.
See these links for some super images and info.:
The cause for the weevils is rot, and the cause for the rot is damp. So - no damp means no rot, and no rot means no weevils.
Thus, some work on your bathroom seem to be necessary:
1) dry out the place and perhaps replace damaged timber
2) make your bathroom "damp-proof"
But not leaving the bathroom wet with the door closed after use is a small start.