These are Lily Beetles, a scourge of southern gardens. You just have to look for them on the leaves of your lilies and squash them between your fingers.

Pick them off and squish them. They tend to fall on their backs and you can't see them in the soil so be vigilant.

Put some white paper around the plants before you start searching for them, that way you can still see them when they drop to the ground, and look on the undersides of the leaves for the grubs, but wear rubber gloves for this, because they live in their own excreta, I know, disgusting, Derek.

Before you kill them all, put a few in a glass, and put your ear close to the glass. You'll be able to hear them squeaking. As Derek says, look for the black lumps of 'poo' on the leaves and remove them, too, because the larvae are hidden in them. The only good thing is that they're bright enough to spot, and the at the first sign of notched edges to the leaves you know they're there, they've given themselves away

Thats a bit horrid Worthy, or should I say not worthy of you!