French Red Underwing Catocala elocata
This central and southern European species has only ever been reliably recorded here once, in 1903, on Jersey, Channel Islands.
Although similar in size and appearance to Red Underwing, C. nupta, there are subtle differences in the forewing markings, and if the hindwings can be viewed, the inner black band is much smoother than that species, which is irregular and jagged.
Abroad, it is fairly common in woods and bushy habitats, especially those bordering rivers. Adult moths fly from July to November. The larvae feed on poplar (Populus) and sallow (Salix).