I am building up a my knowledge of organisms that live on trees (not necessarily as pests, but in the respect of the biodiversity that depend on different tree species) and their interactions.

Living on the underside of Fraxinus excelsior, in northern Europe (N. France), I have found these tiny caterpillars (end of May/start of June). They are eating small patches of the leaf, and excreting black frass.

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The ash leaf in this photo is 70 x 35 mm, and so the caterpillar shown in approximately 1 mm in length, but there are others up to 2 mm.

The photo above also shows the mines in the leaf.

Under a hand lens, the body is an opal/beige colour and it has two black patches on the body above the head. The body is very shiny and glossy and it looks wet.

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From my internet research it looks like a young caterpillar of the Ash Bud Moth (Prays fraxinella)?

  • $\begingroup$ I probably need to invest in a good macro lense for my camera $\endgroup$ Commented May 30, 2017 at 10:46
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    $\begingroup$ Since nobody seems to answer your question, I think you need to wait for another week or two. They will eventually mature and it will be easier to identify them. $\endgroup$
    – banana
    Commented Jun 4, 2017 at 17:03
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    $\begingroup$ Yes thanks, I am keeping an eye on them and will track their progress. I already have a photo of one twice the size which I can add to the post. $\endgroup$ Commented Jun 4, 2017 at 17:16
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    $\begingroup$ Well, that would explain why after returning from France to the UK, I haven't been able to find the larvae here. Perhaps this species has no yet made it across to the UK? I am familiar with ash bud moth, so I would have expected to find the larvae here. Interesting though how the Wikipedia Prays fraxinella caterpillar looks like an older version of the Hungary Forestry Institute images they name Stereonychus fraxini. I'd probably ere on the side of the latter, and agree with you. But yes as @theforestecologist says it would be good to provide some sources to back up your answer please. $\endgroup$ Commented Jun 26, 2017 at 21:21
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    $\begingroup$ I have been doing some further looking into this and came across a video of Prays fraxinella, feeding as a leaf-miner youtube.com/watch?v=LqL6LKEg05k&feature=youtu.be linked from this page ukflymines.co.uk/Moths/Prays_fraxinella.php so yes, this increasingly looks like Stereonychus fraxini $\endgroup$ Commented Jun 26, 2017 at 21:42


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