Return of the Sussex Emerald

Return of the Sussex Emerald
Sussex Emerald Moth

The Sussex Emerald (Thalera fimbrialis) moth is a very rare beast in the UK, with breeding traditionally restricted to the disturbed shingle habitats at Dungeness in Kent (though it has colonised two other sites further east in Kent in recent years).  Adults are active between July and early August and the eggs are laid (and the larvae usually feed) on Wild Carrot, though both Common Ragwort and Hoary Ragwort (and more rarely Yarrow and Gorse) are utilised as a secondary food-plants in the UK. As its name suggests, this species was first found in the UK in Sussex and there were several records around the Beachy Head / Eastbourne area prior to the 1950s. Since then it has occurred only as an occasional immigrant and at Rye Harbour previous to 2019 there had only been two records, with singles on two dates in July 2010.

Carrot 9142 Wild Carrot

Initially, management to encourage this species at Rye Harbour began with the removal of large swathes of Red Valerian which had come to dominate, followed by the by collection and spreading the seeds of Wild Carrot at various points around the reserve, but particularly within the fenced rabbit exclosures on the Beach Reserve, the habitat most similar to that found at its traditional breeding sites in Kent.

 Rxsean and rebecca b  Sean Clancy and Rebecca Levey, with Discovery Centre in background

This effort appears to have paid off and from 2019 adult moths became relatively abundant in the moth trap, with a total of 22 trapped in 2019 and 15 in 2020 and there was a strong suspicion that this species was breeding at Rye Harbour. A search for larvae in May 2020 was unsuccessful, but a return visit by moth expert Sean Clancy and Rebecca Levey of ‘Kent’s Magnificent Moths’ ( on 10th June found two well-grown larvae on Wild Carrot in the grassy area just to the west of the temporary visitor centre, the first ever found in Sussex. At last, the Sussex Emerald really does live up to its name!

 RxThalera  fimbrialis larva b  The first Sussex Emerald Larva ever found in Sussex


  • Shirley Ford:

    16 Jun 2021 11:14:00

    So exciting to the Sussex Emerald in Sussex. Well done everyone who have worked so hard to make it welcome

  • Sharon Sellens:

    16 Jun 2021 11:32:00

    Thank you RHNR for your sterling work xx

  • Eve Montgomery:

    16 Jun 2021 13:43:00

    Lovely to see such a beautiful butterfly return. I’m also glad to see that you have included it’s scientific name Thalera fimbrialis in this article. It’s a pity that the botanical names of the plants are not mentioned as well. I guess plants are not considered to be as important as butterflies.

  • Julia Dance:

    16 Jun 2021 16:24:00

    A heart lifting biodiversity step in the right direction . Well done and thank you.

  • Lucy:

    16 Jun 2021 17:25:00

    I saw one of these last week :) it flew into my house (Lewes) and was on the hallway wall – my kitten was trying to get it and I saved it and took it outside. I had never seen one before and it was very beautiful

  • 16 Jun 2021 18:55:39

    @Lucy – There have been infrequent sightings of Sussex Emeralds over the years, so you may have been lucky enough to see one. There are also closely-related moths, which look quite similar – especially the Common Emerald.

  • Ali shine:

    24 Jun 2021 07:29:00

    I had one very similar in my garden in Lewes. I was told on a moth and butterfly site it was a light emerald. Was wondering how to differentiate?

    ANSWER: There are a number of Emerald moth species, the Common Emerald is most similar to the Sussex Emerald. Sussex Emerald has more distinct red and white chequering along the wing fringe, the hindwing having a distinct concave scallop between two points.
  • Roma Brown:

    11 Jul 2021 12:57:00

    My sister has just sent me a photo of the Emerald moth that settled on a picture she has in her house in Chesterfield Derbyshire
    Date is 11 July 2021

  • Gill Emerson:

    22 Jul 2021 08:14:00

    I think one of these beautiful moths came into my bathroom. I live in Brighton. I took a picture but I’m not sure how to share it for someone to verify. It looks the right shape and colour but doesn’t have the brown edges.

    ANSWER You could send it to our WildCall Officer Charlotte [email protected]
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