Pollen wasp nest

Remember that male Pseudomasaris I found hilltopping last week? Well, this is the kind of nest the female pollen wasp makes. The only species I am aware of that will attach its mud nest to a plant is Pseudomasaris vespoides. This is an old nest, as evidenced by the exit holes (an "active" nest will show no holes). Spiders may have built silken retreats in some of the vacant cells.

Done