Still fairly new to leaf mining, but I have been out a few times recently and found this mine on Hazel.
I have initially identified it as Stigmella floslactella, but the colour of the larva has me doubting this.
The photo is not excellent, but the colours are reasonably true. I would appreciate any feedback.
the mine itself looks ok to me (clear margins either side of the frass) but I'd be wondering about the larva... in floslactella it ought to be pale yellow with a browner head... On the other side of the coin, there's not much that gets on hazel that produce such mines....unless its a fly of some kind.
The other Steve H may have a more conclusive view on it.
I reckon the larva is dead or dying, hence the dark colour. The frass line at the start of the mine looks very thin and black so I would suggest you have S.microtheriella rather than S.floslactella.