Perhaps I may have made such a discovery - a very small one - as I drove along a woods road not far from home.
Again, these are very small moths. P. insignis would be dwarfed by a grain of rice.
I puzzled over these coltsfoot dwellers for awhile and couldn't find answers, so emailed an expert and here is a portion of his reply.
"... There is, however, no published record of this moth mining in coltsfoot, and you may well be the first person to have reared it from this plant. I have been seeing these mines for some time, and had assumed they must be P. insignis, but it's great to have this confirmation."Ahhh, so my coltsfoot dwellers are well known, just not documented in association with the plant from which I reared them. Therefore, I'll publish this little discovery here in hopes that it counts as a 'published record' and adds a tiny bit of info to the body of scientific knowledge.
First, here is a photo of a leafmine typical of the many I have found on coltsfoot leaves (Tussilago farfara). The twisting tunnel of the P. insignis larva is on the upper surface of the leaf.
Here is a photo of a leaf miner larva, P. insignis, as it feeds on a coltsfoot leaf. The mines are exceptionally long because these particular leaf miners feed solely on sap from the damaged leaf tissue.
When the leaf mining larvae are finished feeding and are ready to pupate, they make a kind of three-sided chamber right there on the leaf surface at the end of their feeding tunnels.
The pupal chamber on the coltsfoot leaf pictured below, is very near where the leaf miner started mining the leaf. See the thin trace of the early mine on the lower left of the pupating leaf miner?
Here is another 'volume' written by P. insignis.