Geographic location of the bug: Byrnestown qld. 4625.
Your letter to the bugman: Have had a lovely yellow and black wasp building a very small mud nest on the toilet seat of all places! I have not seen another one like her, there are a lot of the mud dauber wasps that build their nests everywhere in the house, this ones stripes are more yellow than the mud dauber, she was trying to put a caterpillar in the nest but caught me watching her and took off and I haven’t seen her return, usually the mud dauber wasps don’t care if you watch them, actually can get very close, would you happen to know the species?, seems very shy.
How you want your letter signed: Leigh
This looks to us like the nest of a Potter Wasp in the subfamily Eumeninae, a subfamily well represented with yellow and black individuals from Australia pictured on the Brisbane Insect site where it states: “Potter Wasps in Eumeninae build mud nest. They are solitary wasps. They are typically black and yellow or black and orange in colours. Potter wasps usually prey on caterpillars which they paralyze and place inside cells in their nests for their young. Nests are either dug into the ground, constructed from mud, in wood, or in existing burrows of their hosts.”