Another Monday, another leafmine. I noticed this one while checking out Alder leaves to see what small creatures had been munching holes in their leaves (more on those later this week). This blotch mine was made by the larva of sawfly Heterarthrus vagans (you can see what the adult sawfly looks like on the Sawflies website here).

I thought initially this might have been the larva of sawfly Fenusa dohrnii – I was right about it being a sawfly but had the species wrong. Fortunately, I had held the leaf up to the light to get a slightly clearer photo of the larva within as, from looking at that, British Leafminers expert Rob was able to tell me: ‘It has a black “bow tie” … so is a Heterarthrus and as it is Alder it is Heterarthrus vagans‘. Who knew sawfly larvae wore bow ties? But it seems all the Heterarthrus species larvae have them. Very smart!