In a dark fantasy I'm doing, I want the castle to have creatures (rodents, insects, pests in general) you would typically find (But, of course, altered in very odd, sometimes grotesque ways). I'm assuming things like rats and spiders wouldn't be uncommon, but I know very little about what pests might actually inhabit a castle.
So, what kind of pests might one encounter in a typical medieval castle?
Other things to consider, what is the landscape around the castle like? Mountainous, prairie, forest, desert, that would depend on what pests one might find as well.
[This message has been edited by Strychnine (edited August 12, 2010).]
I was going to say bats maybe in the towers. I can see birds, too. Those windows, even if they were slits, wouldn't have glass, after all.
Definitely rats and mice.
Since "mattresses" are probably straw-filled ticks, all kinds of things might live in there. Especially bed bugs. (EWW!)
Fleas from the dogs (and the people).
I've read somewhere that cats and foxes were also considered pests. I'd expect mammals that size would have been more common on the castle grounds rather than inside, however.
[This message has been edited by aspirit (edited August 13, 2010).]
Pests also come in with supplies.
Disease is also rampant, though not a visible pest. Microorganisms carry disease - not just the well known stuff like smallpox, but also common colds, diarrhea, etc...
Don't forget mythical pests, like the garden gnomes in Harry Potter. You could have pygmy dragons or rebellious gargoyles causing problems.
Also pay attention to the climate where your castle is located. A medieval English castle will have rats and bugs and bats. A castle in ancient arabia will have spiders and scorpions and snakes and stuff.
I like the idea of mythical pests. There's some good fun you could have there with the idea of something like a centipede or a bat, then twist it to make it fit your story...
Also keep in mind that there would always be dogs around, which would keep most of the rodent population in check. Not bugs, necessarrily, but rats and mice would try to stay away from even the smell of dogs. It's just a thought.
Good luck!
If we are assuming your "medieval" castle means a broadly European fauna, then you will have huge numbers of invertebrates, and large numbers of small rodents. Dogs and cats may well keep the rodent population under some kind of control but they will very definitely be present in significant numbers. Birds are unlikely to make much use of inhabited/heavily used buildings but will next in unoccupied areas; likewise bats. Swallows and martins will likely nest on the outside of the castle if it is in a farmed area (pre-pesticide farms = insects; insects = swallows); likewise sparrows will be somewhere around but probably not in big enough numbers to be considered a pest (grain pests are mice and rats, which was why granaries were often raised on mushroom stones to stop them from climbing in).
Four-poster/canopy beds were originally designed to prevent bugs and droppings and the like falling on the beds from the roof (which would not have been plastered), which says something about how prevalent pests were.
If your castle is in less traditional fantasy climes, you are at liberty to have scorpions, giant centipedes, snakes, lizards, cockroaches, praying mantises, termites and more as potential problems.
[This message has been edited by Corky (edited August 16, 2010).]