A small sign attached to is says that it is part of an insect monitoring project of the Pennsylvania Department of Agriculture.
Since it is hung from an ash tree I assumed they are monitoring for emerald ash borer, a destructive insect pest that just showed up in Pennsylvania last year. The PDA website indicates that the traps are being deployed on 1.5 x 1.5 grids in 35 counties. Emerald ash borer was probably imported in solid wood shipping pallets from its native Asia.
Inside the panels is a chemical that mimics those given off by a dying tree. This attracts insects that make their home in stressed or dying trees, which then become trapped on the sticky panels.
Let's hope the researchers don't find the emerald ash borer here. EAB has the potential to remove ash as a component of the forest, dramatically changing forests wherever it becomes established.
The most important thing you can do to prevent the spread of emerald ash borer is not moving firewood.