Moved from ID Request.

In this photo, on the top leaflet, the white area is a leaf mine of Macrosaccus robiniella (Gracillariidae), the larva of which can form its mine on either the upperside or the underside (as seen here) of a leaflet. The brown track of skeletonization that was associated two leaflets being silked together is the larval damage of a gelechiid, most likely Sinoe robiniella. The brown color of the damage indicates that it was done some time before your photo was taken. This describes a scenario in which the Sinoe larva (which is very small) finished feeding and exited the leaflets in order to pupate. Alternatively, however, this could be abortive damage made by the larva of another leaflet-tying/skeletonizing gelechiid, Filatima pseudacaciella, which in its final instar is much larger than S. robiniella.

The area of damage seen on the bottom leaflet is an upperside view of a Macrosaccus robiniella mine that was made on the underside of that leaflet.

In your second photo linked here, the white area is a mine of Macrosaccus robiniella, in this case made on the upperside of the leaflet, alongside gelechiid-produced skeletonization damage as explained above.