Elachista subalbidella mine

While looking (unsuccessfully) for Marsh Fritillary webs on Llantrisant Common on Tuesday I chanced across this occupied leaf mine on Purple Moor-grass Molinia caerulea. There is only one species of miner known from this plant, Elachista subalbidella, and the larva matches the description in MBGBI vol. 3, so I think the identification is safe (I'll try and rear the adult but don't fancy my chances). I can't find any online images of this mine so I guess it's not often seen in the larval stage.