I don’t know about you but when I see a leaf with holes in it, I feel a compulsion to turn over that leaf to try to determine what caused those holes. And that’s how I discovered today’s rather bizarre-looking creature.
And once I realised that the holes it made were smaller than many of the other holes in the surrounding leaves, I looked for other leaves with similar sized holes. And so I found several more.
And then I looked at other Alder trees in the same park, and I found even more.
It took a bit of googling when I got home but I eventually found a name for my mystery creatures, and that identification has now been confirmed by a national expert. These are the larvae of a sawfly called Platycampus luridiventris, a rather non-descript fly when you consider the larva it develops from. You can see that adult fly and read the scientific information about this species on The Sawflies (Symphyta) of Britain and Ireland website.