I have a numnber of plants in containers in my garden, including a small herb selection - basil, chives, thyme, parsley etc. They are all untouched except the basil plant which has been eaten alive! Several of the leaves have chunks taken out of them. i have carefully inspected the plant, pot and surrounding area but cannot see anything at all. We don't seem to have a problem with slugs/snails - I've only seen one or two in the year we've lived here. What is most likely enjoying the fruits of my labour, and how can I prevent it? Thanks!