As autumn colours sweep through our woodlands, there is still a flash of brilliant green to look out for. October offers one of the last chances of the year to see the Merveille du jour, regarded as one of Britain’s most beautiful moths. With its jewel-like colours and extraordinarily detailed markings, it is easy to see why. 

The Merveille du jour wings display an incredibly intricate pattern of emerald, mint and sage green, broken up by flashes of black, white and grey. These colours extend across the moth’s ‘fluffy’ thorax and head, completing the pattern. This beautiful mosaic has earned the moth its unusual French name: ‘wonder of the day’ and is essential for survival. The varying shades of colours provide the perfect camouflage, allowing the moth to disappear among lichens growing on tree trunks and branches.

The moth can be found throughout Hampshire, although its population is thinly spread. It favours established woodland with plenty of mature oak trees, which play an important part throughout its life cycle. 

The adult moth lay eggs on oak trees, where they remain over winter before hatching the following spring. The caterpillars rely on English and sessile oaks as food plants, feeding on their flowers and leaves throughout the summer until they are ready to pupate. 

The Merveille du jour has some clever ways of staying hidden before it even becomes an adult moth. As the caterpillars grow, they feed on the oak leaves under the cover of darkness, retreating during the day to hide in crevices in the tree’s bark. Once fully grown, the caterpillar leaves the tree and heads underground, where it spins a tough cocoon before eventually transforming into the spectacular green adult that emerges in autumn.

It is one of the UK’s later-emerging moths, typically flying from September to late October, although in warmer years it can remain on the wing into November. Look out for it around flowering ivy and overripe fruit where adults stop to feed before their brief autumn appearance comes to an end.