In the world of moths, leaf-mines are highly regarded. The patterns created and the tree species with which the mine is associated are unique to each species, meaning that larval workings provide the most hassle-free method of identifying many otherwise problematic groups (i,e. genus Stigmella & Phyllonorycter).
Some are harder to find than others, but rummage through a large deciduous tree and you'll quickly tally up a good list of species...
|Stigmella tityrella on Beech|
|Stigmella oxyacanthella on Hawthorn|
|Stigmella hybnerella on Hawthorn|
|Stigmella anomalella on Rose|
|Leaf-mining at the foot of the Malvern Hills|
|It was foggy|