From butterflies to wasps! As we sat on our front porch eating lunch, we could hear a distant buzzing. On investigation we found mud dauber wasps making nests in two holes drilled into the top of the window frame which had obviously once held the ends of a dowel or curtain rod.
The first photos below shows one hole with a partially constructed nest.The dark-coloured wasp is barely visible at the lower left of the picture. The second photo shows the other hole with a completed nest inside.
A little research tells me that these are solitary wasps, not aggressive, only stinging if they are under threat, so we'll leave them be.
They use their sting to paralyze spiders, carrying them back to the nest and laying an egg on top of each one. When the larva hatches, it eats the spider. Seeing that most Australian spiders are dangerous to humans, mud wasps would appear to be on the whole beneficial insects. Adult wasps prefer nectar to spider meals.