Near the causeway I found a few more mines - including this possible identification of the moth caterpillar Phyllonorycter kleemannella = klemannella (The Dark Alder Midget). The season is only right-ish (mines are supposedly found in May/June and July/August with a possible third generation) but it is supposed to be a common species, and it cannot really be anything else! The caterpillar is supposed to attack the Common, Grey and Italian Alders in the UK, but not the Green Alder. This is a rather poor picture of the mine on the underside of the leaf, not very large, and certainly not extending the majority of the distance between midrib and leaf margin. Just visible near the top are three small creases?
and these pictures are of the larva extricated from the above mine, which is pale and typical of all the Phyllonorycter species except Phyllonorycter froelichiella, where the larva is grey. Once the larva pupates it is found in a white cocoon attached to the roof of the mine, well away from the frass piled in a corner. Before emergence the pupa wriggles to be partly sticking out of the mine, ready to emerge!
and the sawfly Heterarthus vagans on Common Alder, Alnus glutinosa. This common sawfly caterpillar is supposed to attack the Common, Grey and Italian Alders in the UK, but not the Green Alder.
This is probably the pre-pupal stage of Heterarthus vagans, extricated from an apparent pupation disc of the large brown mine of rather indeterminate shape. There appeared to be several discs on the leaf, but actually only one live insect. However the guides suggest that there is normally only one mine per leaf.
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