The word acarodomatium means something akin to ‘house for mites’. The term is used for structures in plant leaves that seem to have been developed to enable mites to withdraw, or even establish. The best known acarodomatia are the hair bundles in the axils of lateral veins, like for instance in Lime. Thick veins can be widened to form a sort of side shelter (often in Hawthon), or intricate flaps (like in laurel leaves, look in the kitchen). The assumption is that the acarodomatia are advantageous for plants because they especially harbour predatory mites, that hunt for spider mites and young stages of insects like thrips. It appears that also vacated mines play a role as acarodomatia, because when opening an old mine very often mites are seen inside.
An interesting aside is that also gall mites, Eriophyidae, now and then may profit from the presence of mines. In the blotches of Phyllonorycter platani on London Plane a specialised gall mite has been discovered that within the protection of the mine feeds on the cell sap of the leaf parenchyma (Domes, 2002a).
It is very remarkable that mites do not make mines. The Acari are an extremely varied group, and it is difficult to think of an adaptation that has not been ‘discovered’ by them. In fact, they have discovered the mining way of life, not on plant, but on mammals: scabies is essentially not different from a mine in mammal skin.