They are a very good idea.

We have a small cane home for solitary bees and others attached to the garage wall, and a branch & twig pile in the far corner of the garden for hedgehogs and anything that needs it.

There is a seriously palatial edifice in a neighbour's garden, complete with holey bricks supporting it off the ground, and one in a flower border by the sea.

The town is taking its insect life seriously! As Madeleine says below, we need to!