Leaf-mines on Aspen

Now is a very good time to be looking for mines in "green islands" on fallen leaves.  Last night, during what was probably my final monthly visit this year to a wood in Yardley Chase in the far north of Bucks, the first moth into one of the traps was a Clifden Nonpareil, not unexpected because the site has plenty of aspen which is the moth's preferred larval food-plant.  Half an hour spent rummaging through fallen aspen leaves while awaiting the next arrival (...yes, it was quite slow for adult moths!) produced many examples with these "green islands" emanating out from the petiole and all of them showed the mines of Ectoedemia argyropeza in various stages of completion.  The egg is laid on the leaf stem and the larva initially forms a gall in the petiole before working its way up into the base of the leaf to create a blotch mine.  Of half a dozen leaves brought home last night, all of which contained active larvae when collected, this morning I could find only one with the larva visible so they must be able to retreat into the petiole during the daytime.  

Aspen leaf showing a typical "green island"

Same leaf showing start of mine in "green island"
(no larva visible)

Different leaf with a more well-developed mine
(larva visible)

It is the larva itself which provokes a chemical reaction in the decaying leaf to ensure that it has sufficient food to complete its development.  Fallen leaves of Black Poplar are also now worth inspecting in the same way for similar evidence of the closely-related Ectoedemia hannoverella.  This species has yet to be found in Bucks, despite the county having huge numbers of the tree, so you could make a name for yourself by getting the first record!

Apart from the Clifden Nonpareil last night there was little else amongst the adult moths to comment on other than a welcome sighting of the rather nondescript dark tortrix Epinotia maculana (another aspen feeder) and the appearance of the first Epirrita species I've seen this season.  Two males of November Moth were recorded (both checked).

Epinotia maculana, Yardley Chase 6th October

November Moth, Yardley Chase 6th October

Dave Wilton Westcott, Bucks