More of an impish grin really. Unless of course she’s popping out an egg or two and it’s a grimace.
Holly seems like a tough food plant for such a delicate creature, but apparently the caterpillars prefer the flowers to the leaves which, judging by the number of buds on the holly right now, they won’t be short of.
Unusually for butterflies, Holly Blues lay their eggs on a different food plant, in their case ivy, for the second brood in the autumn. Conveniently, ivy flowers at that time of year so the caterpillars can nibble away on flowers in the autumn as well.
This particular Holly Blue female was flitting around a tall Holly Bush at the end of the garden and being pretty indecisive about where or when to land. When she eventually did, she was good enough to find a sunny spot which illuminated her against the shadows. Here’s another shot, this time face on.
You can see from the size of those holly leaves just how tiny these butterflies are.