Small but silver

More unsettled weather, though the winds have died down. So only a few moths, and most of them predictable. This one interested me, however: it's only a Silver Y (I'm 90 percent sure, although I get muddled by the rather similar Golden Y and Beautiful Golden Y), but it seemed unusually small.

Since you may not be familiar with the size of a Sainsbury's 'Taste the Difference' eggbox, and since the moth was peacefully sleeping, I took it inside and lined it up with Penny's old printer's ruler, from her days as chief sub-editor of Cosmopolitan. I could give you the measurement in points, but here it is in millimetres: 15.

This suggests a Silver Y, whose forewing length is 13-21mm according to Waring, Townend and Lewington whereas the other two start at 17mm. Aren't I getting scientifc in my old age? Note, though, the different effects of light (a) outside and (b) in our kitchen. It reminds me of a mirror I once had in a hotel in San Francisco which showed how you looked in daylight, bright office light and subdued restaurant light. As I recall, the last was the most forgiving. Update: see very helpful comments which suggests that this is indeed a Silver Y, a small version due to starvation as a caterpillar known as 'gammina'.