- "Xestia rhomboidea" and variants redirect here; these names were for long misapplied to the Square-spotted Clay (X. stigmatica).
Phalaena (Noctua) rhomboidea Esper, 1790
This species has pale brown forewings marked with two distinctive black marks. Despite the common name, only one of these is square, the other being roughly triangular. The hindwings are similar in colour to the forewings. The wingspan is 36–46 mm. The moth flies at night in June and July in the British Isles. It is attracted to light and sugar and to flowers such as wood sage.
The larva is brown with black marks and is polyphagous, feeding on a wide variety of plants including birch, blackthorn, bramble, dock, hawthorn, raspberry and sallow. The species overwinters as a larva.
- Chinery, M. Collins Guide to the Insects of Britain and Western Europe. 1986 (Reprinted 1991)
- Skinner, B. Colour Identification Guide to Moths of the British Isles. 1984