tree bumblebee nest and wax moths

Our tree bumblebees have gone thanks to Wax moths, Aphomia sociella. I was not sure what was going on having never seen inside a bumblebee nest, but the nest went very quiet in mid July and so Rupert had a peep, the lid of the nestbox was stuck down quite tight with silky threads and there were white grubs/caterpillars amongst the threads. One or two bees were still hanging around and Rupert is pretty sure that one squirted him with something in defence - enough to make him get down the ladder quick and not to want to return to take a photo! At first we thought they must be bee grubs, but knowing bees don’t make silk it seemed a bit odd… so a bit of a search and it seems that it must have been these moths, or their caterpillars at least. According to www.bumblebee.org in northern Europe the wax moth is regarded as the most serious enemy of the bumblebee, and is found only in bumblebee nests. In some areas in southern England as many as 80% of nests can be destroyed. The adult moth flies from June - August. It enters the bumblebee nest and lays her eggs, at first the caterpillars feed on nest debris, but as they grow they switch to feeding on the wax food cells, food stores and even larvae. Normally this destroys the nest. The moth leaves the nest to overwinter as a pupa in a sheltered spot, It spins a strong, brown cocoon in autumn. Wonder if our bees will return next year?