I see user Greg Dodge has already started the discussion about what agent made mines like these in White Clover. I applaud his efforts to rear some as I am in no position to do that at the moment. From what little I could find online suggests the mines look much more like the ones created by the South American cousin (=minuta) of our North American native moth [=desmodiella) in the genus, Porphyrosela. I see that Greg also flirted with the same notion.
[See photo on: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1519-566X2007000400005
In addition to what has already been discussed regarding these leaf mines I would like to add the following comments/anecdotes:
1. Until this year I do not recall encountering such incredibly conspicuous leaf mines on such a common plant given how much attention I pay to its flowers in my searches for pollinators, especially bees.
2. And factoring in how incredibly common these mines were on the White Clover plants growing only a couple feet from the back door of my house it seems fairly unlikely that I simply overlooked them previously, especially considering I've been photo-documenting what lives in my watershed for the past 6-7 years.
Not sure if any of this helps but I look forward to learning more about what made these.