Aptura ilia flies from May to September in one or two generations.
   It feeds on tree honeydew and flies near their summit. It goes down only to find moisture, honeydew shrubs or excrement.
   The eggs are laid singly on leaves.
   The caterpillar host plants are willows and poplars, in particular Populus tremula and Populus nigra. They either pupate in the same year or winters as young caterpillars, becoming brown, and stuck to a twig.
   The grey green chrysalis hangs from a leaf or twig.
  The ventral side of the wings is dark brown, with metallic blue violet hues in the male, and it has a clear postdiscal band on the hind wing and several light spots on the fore wing. These clear areas can be presented in two different aspects; they are white on the butterflies of the nominal form ilia, and clear fawn in the form clytie. For both forms, the fore wing also has an orange-coloured ocellus, which makes differentiating the species from Apatura iris possible.
   A similar ocellus is present on the hind wing in both species. The reverse side of the fore wing is brown and the back of the hind wing is dull brown with, as in A. iris, an orange ocellus centered in black.
   Distribution ranges from northern Spain through central Europe (south to the Mediterranean Sea) and temperate Asia to China.