Are you finding bits of your conifer trees dying back and inside there are strange clumps of detritus among the branches? If you open the clumps you will find that they contain caterpillars that are munching on your conifer and killing the tips causing browning off and dieback. There may also be white fungal hyphae where the detritus is beginning to decay. The clumps of dead and live foliage, frass (faeces) and other material are held together by silk webbing produced by the caterpillars. The caterpillars feed on the live and dead foliage.
The communal clumps are built by the caterpillars of the Gregarious tineid, diurnal oecophorid moth (Hierodoris atychioides). In autumn the caterpillars within may all be small young instars (stages) that will remain in the protective clump to survive the winter. There may also be caterpillars of other species found in the clumps.
Note: Bagworm moth caterpillars produce similar clumps of detritus, but these are individual and hang like a bag from the foliage of the tree.