If it is a fantastic inspector, I'd pay for the pest inspection.
But know this:
Mice have very thin crusty poops. They aren't always perfect hamster style poops.
Think of a piece of Uncle Ben's rice that had been parboiled. Then painted dark brown / black.
If you get up in the attic, use a strong flashlight.
A trained eye can find all sorts of pest sign.
The BEST trick is to open the attic hatch, and put 2-3 mouse traps with peanut butter soaked bread packed into the trigger mechanism.
The bread will go stale, and lodge into the trigger, and still have peanut butter on it.
Leave it up there for a week, then just poke your head up, and there is a 99% chance that if you have a mouse problem, you'll find a dessicated mouse dead in one of the traps. But this only helps if you already own the property.
Carpenter Ants tend to like houses with overhanging trees like a pine, and they go after rotten wood more.
If you have a good roof, and a good sound basement, these details are an added bonus if you can spot them before you purchase.
But, if you go along with the Inspector and inspect the house yourself at the same time, go very slow and you'd be amazed what you can spot, and smell mold, see cracks etc.
Go into a house purchase with eyes wide open, and directly ask questions that concern you.
Do you have a pest problem? Does the roof leak? Does the basement get damp from heavy rain?
Most people will tell the truth and be adverse to telling a direct lie to a direct question.
Make a huge list of questions that concern you, and patiently ask each one to the seller. It may point you into the right direciton, but still keep your wits about you.
If the inspector finds mouse sign, have him document it.
I have walked away from a house that I made an offer on that the inspector found evidence of black mould.
We just walked away, we didn't feel like figuring out the source of the mould problem, so we walked and the Seller didn't have much to hold us to, so it is good to document "deal breaker" flaws.
If you get a home inspection done, inspect the house at the same time that the Inspector is there, it will give you the much needed time to "know" the house.
2-3 hours of poking around and no major issues found will make the stresses of signing at the Lawyers a lot less stressful.