Moths use their proboscis like a straw, to suck up fluids (normally nectar). When not in use the proboscis coils up between the moth's palps.
The Silver Y (Autographa gamma) is named for the marking on its wings, which looks like the latin letter Y or the Greek letter γ.
It normally feeds from flowers, and can often be seen around dusk, though also flies both during the day and at night.
2 images focus stacked manually in Photoshop