Hello! Does anyone know what could be munching my pansy flowers? I can't find any evidence of pests on the plants 
They're in a pot on the table at present. No evidence of slugs (I've painstakingly checked the plants and there are no trails). The foliage is untouched.
The flowers are almost entirely devoured, only the centre is intact. I've noticed some of the buds are getting scoffed right before they unfold, so what's left is a frilly mess upon opening.
I thought googling would offer an obvious explanation but I'm stumped!