What Kind of Hawk Moth?

What Kind of Hawk Moth?

Observation - What Kind of Hawk Moth? - Global. Description: Large Plump green Caterpiller with Purple spots and spiked tail. Feisty when disturbed - rearing up and swinging head about. On ground under tree which was either White Poplar or similar. See photo. Help on ID anyone?

Large Plump green Caterpiller with Purple spots and spiked tail. Feisty when disturbed - rearing up and swinging head about.
On ground under tree which was either White Poplar or similar. See photo. Help on ID anyone?