I believe these mines are made by a fly larva. They are really striking. See how the mines get broader as the larvae get older and fatter!
No interactions present.
According to the British Leafminers website there are two closely related flies that make these sort of mines on Sow-thistles (they also utilise many other species of plant), and their mines are not distinguishable (they can only be told apart by dissection of adult males). The two species have been lumped together under the aggregate name Chromatomyia 'atricornis'.
Do we know which Sow-thistle this is?
Entomologist and biological recorder
I think it is Sonchus oleraceus
University of Edinburgh and Biodiversity Observatory (OU)
Yes, absolutely atricornis.
Before posting my own I visited every post of Chromatomyia 'atricornis' to see if I could learn more - I did. But like every good iSpotter I have returned to agree where possible.
Now my ID is NOT a challenge but an attempt to bring the ID Panel to life. Agreeing to a flawed ID panel is not desirable where there is a good alternative..
So why not look at mine http://www.ispotnature.org/node/740413
Lat/Lng: 52.0, -0.8
OS grid ref: SP8837