About Lithosia quadra (Linnaeus, 1758)
Technical description and variation: Males are much smaller than females. Males are brown-grey with a leaden gloss; their thorax and the base of their wings are golden yellow, and the costa has a metallic blue-green color at its base. Females are yellow, and their forewing has a black-blue spot behind the centre of the costa and above the inner margin. The Japanese form, dives Butl, is said to have darker males, but comparison of a large number of specimens shows this difference is not constant. European specimens vary considerably: females vary in size, and males vary in colouring. In exceptional female cases, one of the spots (ab. unipuncta Spul.) or both spots (ab. impunctata Spul.) may be absent, or the spots may be replaced by a transverse band (ab. fasciata Spul, confluens Dumont).
