Laothoe populi

The Poplar Hawk-moth - Laothoe populi - from my garden in the UK.

It is distinctive due to its habit of resting with its hindwings held further forward than (but still half hidden by) the forewings.

Adults may be seen from May to September, and amazingly do not feed, not having a functional proboscis. The larva is a funky green - a technical term - and feeds on poplar and some other tree species, and pupates below ground.