That's the "scary hole". Shine a torch in there at night and the interior appears to be a large void. The scary bit is the screw jack for the stabilizer which you'll see to the rear of the void. It doesn't look big enough nor does it look as if it connected to much. To think that the whole tail (and therefore the entire aircraft) is dependent on this feeble component is VERY scary. However, if you shine a torch so you can see towards the front you'll see why it is open. The outflow valve vents into the void which this mesh covers.
PM