Animal photography: why so busy?

Can you spot them? They live in trees and are known for their unique nest building behaviour where workers construct nests by weaving together leaves using larval silk.

They are highly territorial and workers aggressively defend their territories against intruders. Because they prey on insects harmful to their host trees, they are sometimes used by indigenous farmers, particularly in southeast Asia, as natural biocontrol agents against agricultural pests.

So what are they?