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Thursday, 28 March 2013

New British tree-moth combo?

While walking in Southampton's parks a couple of days ago, I noticed the impressive Cork Oak (Quercus suber) that grows near the Titanic memorial. As you can see, it's a fine multi-stemmed specimen with the deeply creviced corky bark you would expect, and evergreen leaves with small, short-spined lobes.

Cork Oak (Quercus suber) in East Park, Southampton
Cork Oak (Quercus suber) bark - definitely corky!
Leaf of Cork Oak (Quercus suber) - note the small spined lobes.
Not all the leaves were so pristine however - some had brown patches which, on inspection, were clearly leaf-mines. As Q. suber is non-native and only found where planted such as in this city park, I felt it was worth investigating in case something interesting was present. This is what I found:

Q. suber leaves with mines (spines/lobes rolled inwards and hence not visible)
Mine on Q. suber leaf. The red arrow points to an exit hole. The black arrow points to another hole wihich might be an entrance, or simply an artefact of drying/curling.
Mine on Q. suber leaf. The lighting angle has been changed and the main gallery is clearly visible running from right (by the petiole) to left.

Q. suber leaf showing little evidence of the mine, unlike the upper surface where it is clearly visible.

Backlit Q. suber leaf - the mine is largely full of frass, though the section leading to the exit hole is visible as a short white part of the gallery near the bottom.
So, the mine can be described, but can it be identified? There are numerous leaf-mining invertebrates recorded from Quercus spp. in Britain, but few from evergreen species (which are non-native), and most of those are from Q. ilex. One thought was that it might be Ectoedemia heringella (a moth of the family Nepticulidae which produces multiple mines and can be common in the Southampton/Solent area) but looking here and in Heath (1976), its mines are narrower and more tightly convoluted ('wiggly'). However, it does match Stigmella suberivora (also Nepticulidae) as seen here and again in Heath (1976), plus a brief description in Emmet (1988).

If this is the case, it is an interesting find because, as far as I am aware, although S. suberivora is found on Q. suber in continental Europe (hence the specific name), it has only been recorded from Q. ilex in Britain according to both Ford (1949) and Emmet (1988). Its identity is currently under discussion on iSpot, although to be certain, it may be necessary to revisit the tree to find eggs and/or larvae and raise adults for identification. If confirmed as being S. suberivora on a previously unrecorded host for Britain, I'll post an update here (and undoubtedly write it up more formally for publication!)

References

Emmet, A.M. (1988). A Field Guide to the Smaller British Lepidoptera (2nd ed.). BENHS, Reading.
Ford, L.T. (1949). A Guide to the Smaller British Lepidoptera. SLENHS, London.

Heath, J. (ed.) (1976). The Moths and Butterflies of Great Britain and Ireland. Volume 1: Micropterigidae - Heliozelidae. Blackwell, Oxford / Curwen, London.

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