Like London Buses...

...you wait for ages then three come along at once.  I've never found Stigmella assimilella an easy leaf-mine to locate despite there being plenty of aspen locally.  A quick look at a young sapling on the old land-fill at nearby Woodham, Bucks early this afternoon produced the usual plethora of grazing signs everywhere but then I spotted the obvious mines below, three active ones on the same leaf:

Dave Wilton
Westcott, Bucks