The New Zealand Mason Wasp (sometimes called the Mason Bee) builds nests of clusters of mud cells or tubes.
Identify the problem
Mason Wasps are black, 10-15 mm in length and look a bit like soldier flies. Their mud cell nests are often found packed with immobilized spiders that the mother wasp has caught and are live food for the wasp grubs in the mud cells. The nests are often found on walls, in cracks and crevices or occasionally on curtains and other fabric items. Adult mason wasps feed on nectar and are not likely to sting.
This pile of immobilised spiders was found under the broken mud cell nest above.
Mason Wasps (Pison spinolae) are not regarded as pests except where their mud nests cause a problem such as when they are built in a keyhole.
Did You Know
It is usually orbweb spiders that the female wasp collects to seal in the cells with her eggs.