Return of the Scarlet Lily Beetles

I don't grow lilies as a rule, mostly because they're always ravaged by lily beetles. This year I couldn't resist buying one cut price bulb, which has been growing in a pot on the patio and has just developed some promising looking buds. 

This morning I found three lily-beetles in residence, and they'd probably been there for a while given the state of the leaves. It's remarkable how efficient they are at finding lilies - this one plant is tucked in a corner of our large garden with no other lilies nearby. I know I should probably kill them, but the entomologists in the house like the beetles more than the lilies, so I expect they'll stay. And I probably won't be buying any more lily bulbs...