Wasps in Carpenter Bee burrows

Split main trunk of Ficus sycamorus, 7m above ground. Carpenter Bees made burrows in dead wood. Burrows used by these wasps, body length varying between 25 and 30mm. The wasps seem to eventually take over a section of the Carpenter Bee tunnels, then seal it off with mud. Wasps only arrive with more mud, no prey items. They possibly parasitise on the Carpenter Bee larvae. Wasps are same colour as the Carpenter Bee females.