Swarms advice

[NOLA Chris]

HI,
planning on running a module for the group,
one encounter can cast Creeping doom and insect plague.

Would you allow the two swarms to co-occupy a square?
The creeping doom centipedes are on the ground,
the insect plague wasp swarms are flying.

Since they are both summoned by the same creature,
would they ignore each other and their effects stack against
the characters?
(6d6 of swarm auto damage...plus poison, plus distraction)

A pretty nasty villain, and a mean encounter set-up
(10 foot wide corridor filled with obscuring mists)
where this guy appears
but it is a group of 12th-13th level characters...

appreciate the help!

[Rogar Stonebow]

Well considering swarms of dimunitive or smaller are immune to melee damage, if both are of that size or smaller I would allow it.

[Starglim]

A swarm can occupy the space of any creature. If it does, it deals swarm damage to that creature.

[Devilkiller]

I've generally seen people disallow the stacking of two similar swarms to generate more damage. If that's how you're playing then I think there's little reason why using different types of swarms would make the damage go up.

I think there might actually be a rule about swarms of the same type not stacking, but I'm not sure if it gives a reason. If you need an explanation of why two swarms aren't better than one maybe it could be that a PC can only be covered by so many biting insects at one time.

However you decide to go with this remember that if you have any PCs who can't fly yet pit traps and spells can be great fun, especially when combined with swarms.