Cinnabar Moth on the Sefton Dunes: The Most Striking Insect of the Summer

1 June 2026

The Adult Moth

The cinnabar moth (Tyria jacobaeae) is one of the few British moths that flies readily by day. The forewings are dark grey with two red spots and a red stripe along the outer edge. The hindwings are a vivid crimson red, visible in flight as a flash of bright colour against the dune vegetation. The wingspan is around 32-42mm.

The red and black colouration is aposematic: it signals to predators that the moth is unpalatable. Cinnabar moths accumulate toxic alkaloids from their ragwort foodplant and are genuinely distasteful to birds. The warning colouration is effective and the moths are largely ignored by predators that have learned to associate the pattern with an unpleasant experience.

Adults are on the wing from late May through July, with a peak in June. They fly in warm sunshine but are less active in cloud. You will find them nectaring on ragwort, knapweed, and other open flowers in the dune slacks and on the dune slopes.

The Caterpillar: Even More Conspicuous

The cinnabar caterpillar is arguably more striking than the adult. It is banded in bright orange and black, warning colouration again reflecting the toxic alkaloids absorbed from the ragwort it feeds on. Caterpillars feed gregariously: you will often find groups of 10 to 20 on a single ragwort plant, stripping it down systematically.

The caterpillars are present from July onwards, peaking in August. They are easy to find: look for ragwort plants that have been heavily defoliated, then check the stems carefully. The banding makes them visible from several metres.

Ragwort is the primary foodplant. The moth has a very close association with ragwort populations, and where ragwort grows freely on the dunes, cinnabar moths follow. The Sefton Coast dune system has excellent ragwort populations in the less managed areas, which is part of why the moth does well here.

Where to Find Them

Any area of the Sefton dune system with established ragwort is worth checking. The less intensively managed sections of the dunes, away from the main beach access paths, often have the best populations.

Ainsdale Hills and Birkdale Hills are consistently productive. Walk the dune grassland areas rather than the main paths and look for ragwort in flower. Adults will be nectaring on the flowers. Caterpillars will be on or near the same plants from July.

The best time of day for adults is mid-morning on warm sunny days, when they are actively flying and nectaring. By afternoon they may be resting lower in the vegetation.

The Ragwort Question

Ragwort has a complex reputation in Britain. It is toxic to horses and cattle when consumed in quantity and is subject to control requirements on agricultural land. On the Sefton Coast dunes, away from grazing animals, it is a key plant for a wide range of insects including the cinnabar moth, common blue butterfly, and dozens of other species.

Natural England's management of Ainsdale NNR takes a pragmatic approach: ragwort on the dune system is managed to maintain habitat diversity rather than eradicated. This is the right approach for biodiversity and means the cinnabar moth population remains viable.

If you want to understand why ragwort management on nature reserves is more nuanced than the public narrative suggests, watching a colony of cinnabar caterpillars methodically strip a plant is a good starting point.