I'm using this post to organize information about an unknown species that is widespread in eastern and central North America, making communal blotch mines at the tips of Commelina leaves. So far I have been sent adults reared in Nebraska (but in poor condition), and adults have been reared in Texas but not sent to me; additional specimens would be most welcome!
ARIZONA
https://www.inaturalist.org/observations/101573782 (empty in early August)
IOWA
https://www.inaturalist.org/observations/126396442 (occupied mine in early July, Commelina communis)
MARYLAND
https://www.inaturalist.org/observations/135741747 (empty in late July, Commelina communis)
MASSACHUSETTS
https://www.inaturalist.org/observations/84628557 (empty in late June, Commelina communis)
https://www.inaturalist.org/observations/169367198 (empty in late June, Commelina communis)
NEBRASKA
https://www.inaturalist.org/observations/167916326 (occupied mine in June)
https://www.inaturalist.org/observations/52501694 (occupied mine in July)
https://www.inaturalist.org/observations/124321378 (occupied mine in July)
https://www.inaturalist.org/observations/127296313 (occupied mine in July)
https://www.inaturalist.org/observations/174197152 (adults reared in July)
NEW JERSEY
https://www.inaturalist.org/observations/93249167 (empty in late August, Commelina communis)
https://www.inaturalist.org/observations/58989226 (empty in early September, Commelina ?communis)
NEW YORK
https://www.inaturalist.org/observations/171116790 (empty in early July, Commelina communis)
https://www.inaturalist.org/observations/171933959 (empty in early July, Commelina communis)
https://www.inaturalist.org/observations/88375875 (empty in late July, Commelina communis)
https://www.inaturalist.org/observations/127988596 (aborted in late July, Commelina communis)
https://www.inaturalist.org/observations/57349282 (empty in late August, Commelina communis)
https://www.inaturalist.org/observations/57457933 (empty in late August, Commelina communis)
OHIO
https://www.inaturalist.org/observations/122423956 (empty in mid-June, Commelina communis)
https://www.inaturalist.org/observations/88268930 (empty in mid-July)
OKLAHOMA
https://www.inaturalist.org/observations/90184816 (empty in early August, Commelina communis)
ONTARIO
https://www.inaturalist.org/observations/171240729 (empty in late June)
https://www.inaturalist.org/observations/171240726 (empty in late June)
PENNSYLVANIA
https://www.inaturalist.org/observations/83704220 (empty in early June, Commelina communis)
https://www.inaturalist.org/observations/87465352 (empty in mid-July, Commelina communis)
https://www.inaturalist.org/observations/87465504 (empty in mid-July, Commelina communis)
https://www.inaturalist.org/observations/89344660 (empty in late July, Commelina communis)
TEXAS
https://www.inaturalist.org/observations/157203052 (empty in late April, Commelina erecta)
https://www.inaturalist.org/observations/158941750 (adults reared in May, Commelina erecta)
https://www.inaturalist.org/observations/52611726 (empty in early July, Commelina erecta)
https://www.inaturalist.org/observations/87073953 (empty in mid-July, Commelina erecta)
https://www.inaturalist.org/observations/87466107 (aborted in mid-July, maybe not the same thing; Commelina erecta)
https://www.inaturalist.org/observations/191702503 (occupied in late November, Commelina erecta)

Someone just asked me, "Any general advice on distinguishing leafminers from other leaf blights?" I figured it was worth copying my reply here for future reference.

To get a search image, you can peruse the observations in this project:
https://www.inaturalist.org/projects/leafminers-of-north-america
Ideally, anything you think might be a leaf mine should be viewed/photographed from both leaf surfaces in reflected light as well as in transmitted light. If it is truly a mine, it will have both epidermises intact, and it will either contain a larva/pupa or have a hole/slit in one epidermis through which the larva or adult exited. It also will typically have visible frass inside, unless it is a species that expels its frass through a hole/slit in one epidermis.

As for distinguishing leaf mines from other types of insect feeding, it's clear from some of the observations that have been added to this project, or have been given the "leafmine" evidence of presence annotation, that not everyone is clear on what defines a leafminer. Leafmining is not a general term for eating leaves; it refers exclusively to insect larvae feeding inside leaves, between the two epidermises. A hole in a leaf is not a mine, nor is feeding sign with only one epidermis left intact (this is called "window-feeding"). If you see a bug on the surface of a leaf, it is not mining***! If a larva is feeding between two leaves that are tied together, or within a rolled or folded leaf, that also isn't mining (although some mines can cause the edges of leaves to curl/fold).

I made a key to the different feeding modes of herbivorous insects in the third edition of Leafminers of North America, but the information above should be all you need to decide if something is mining or not.

*** (unless it is extending the front of its body into the leaf to feed, as is done by Coleophora casebearers and a few other things.)