What is eating scarlet runner beans?

Would welcome input about what is eating the leaves on my scarlet runners. There is no obvious possible culprit other than the occasional fly which is about twice the size of a fruit fly. There is nothing else around during the day but of course there might be nighttime visitors. Not all of the plants are being attacked yet.

Thanks

Margaret

 

It might be slug damage.

 

Thanks Vitog.
You are spot on as we found a slug having breakfast this morning. It had never occurred to me that slugs are nocturnal but that also explains damage on the hostas.
Margaret

 

Slugs aren't necessarily nocturnal; they just need high humidity. So they will be out during the day in rainy weather and during the cooler, more humid night when days are dry.