Sphingidae ...

Privet Hawk-moth (Sphinx ligustri)

S. ligustri (Linnaeus, 1758) is our largest resident hawk-moth, with a wing span of 100-120mm, and can be found across the southern half of Britain. In Sussex it usually occurs singly or sparingly, though occasionally can be fairly common at mercury vapour light in a wide range of habitats. The adult, which has distinctive pink and black barring on the body and correspondingly striped hindwings (which are typically concealed unless the insect is disturbed), usually flies in June and July. The larvae are even more spectacular than the adult, being bright green with lilac and white stripes along the side, and a curved black horn to the rear. It feeds on privet (Ligustrum), lilac (Syringa), holly (Ilex) and ash (Fraxinus).

This specimen, one of two, from the South Downs today ...

References:

www.ukmoths.org.uk/show.php?id=1669

www.sussexmothgroup.org.uk/speciesData.php?taxonNum=1976