Possible Pest Problem over the Pub

I could have sworn Mr. Underby had the pub sprayed for pests recently.  It’s possibly how Pip “disappeared”.  However, I was cleaning under the rug in my store when I snapped a quick photo of this horrific creature:

I can’t be sure, but it may have hitched a ride home in my luggage from my last visit to Dunwich.  I thought the acid used in Mr. Underby’s Pest Obliteration concoction would kill anything, but apparently not.

And now this creature is in my ceiling, shattering my mind.