it's technically not "beetle poop": shellac is the resin that the *tree* excretes as a response to the beetles attacking it. The tree is trying to heal the wound with its sap as well as cover and kill the pests...as least that's the story I'm told.
Oops: I've been told wrong, it IS secretions of the insect, not the tree(s)...but still, it's not "poop"...maybe more like "sweaty vomit", that's got a nicer ring to it!