I know I should have put the chicken wire fencing up sooner, as a bird, probably a woodpecker or a rat pulled out the top 4 cm of tubes from two of my boxes, Fortunately it never opened all the tubes but a few were broken so I was able to open them and see the larvae stage inside
you can see the larvae attached to the plug of pollen in each section of the phragmites tube. At this stage one should not move or jar the tubes as the larvae can fall off the plug of food. I was able to tape back up the tubes and the larvae inside should survive OK as long as they can reattach to the food pellet.
The solution, 1 inch opening chicken wire:
