beehives

[jfronk]

How do those black bees make those gray hives that hang from trees?

[Clanad]

Their equivalent of spit, actually. What you are decribing must be wasp's nests, which are grey and paper like if you get close enough (not recommended) to inspect them. The wasps chew up wood fibers and mix it with their saliva. The nests aren't reused, by the way... they are rebuilt each season...

[RATTER15]

Spot on Clanad, jfronk is describing a wasp nest not a bee hive