The Food Chain - Part I

I was pleased I'd had some of the lettuce leaves. Rich came in the other day and said, "They're gone!" At the time, that just meant, with holes. The next day it meant stripped entirely.  Eventually, I found some caterpillars and think they're small whites. I was hoping that it would become a butterfly bed until I realised they were still small and they'd run out of food. Plan 2 - add some mustard leaves - some moved in.

I then thought I'd give them an escape route by taking the hanging trough off the balcony and putting it near plants in the garden. I thought they'd made it when I could only find two or three caterpillars.

Until...