Thuja red cedar
See also Platycladus.
Dichotomous table for leafminers
1a larva: head and anal shield black; pupation outside the mine: Argyresthia trifasciata
1b head and anal shield dark brown; pupation within the mine (infested twigs wilt and fall to the ground!): Argyresthia thuiella
1c galls, etc => Tables for all parasites per species
Not included in the key: Argyresthia cupressella.