Clifden Nonpareil

Catocala fraxini

Blue Underwing, Blue Underwing, Clifden Nonpareil, Underwing Moth

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A close up of a Clifden Nonpareil Catocala fraxini moth on some tree bark
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It's thought the moth Clifden Nonpareil gets its name from the location it was first recorded in Britain during the 1800s. They also go by the name of Blue Underwing, which describes the contrasting blue bands on the hindwings, which are only displayed when the moth extends its forewings when at rest. These moths favour broadleaved woodland, with the highest periods of activity peaking in the evenings. Nonetheless, it's still possible to see these beautiful moths resting on garden trees in the day time too, from late August through to early October.
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A beautiful and rare moth that's one of the the largest of it's kind!
This species of underwing is seldom seen, but they will occasionally visit gardens.


Underwing moths possess characteristic wing patterning that makes them easy to identify (Catocala). The forewings are a mottled grey, white and brown, resembling many other species. However, when the forewings become extended they reveal the distinctive black hindwings with vivid blue/ lilac stripes. Females moths are almost always bigger than males. A blue underwing female can have a wingspan as large as 9.5cm. Females can sometimes be seen resting on walls, fences and tree trunks. The caterpillars can vary but generally resemble the patterning seen on the forewings of the adults. These are strongly associated with species within the Populus genus. They can vary anywhere between 4-9cm.


Caterpillars may be seen on the leaves of plants within the Populus genus.











Widespread across Europe but low in numbers.

Biological treatment

These moths are rare and cause no damage to garden plants.

Attracts this pest

These insects will feed on plants of the populus genus as caterpillars switching to nectar-rich flowers when moths!
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