A rounded rosette gall formed from leaves and buds at the shoot-tips of wild Thyme (Thymus polytrichus).  The mites live inside the long dense white hairs on and inside the gall.

Photograph the gall in situ; ensure you have noted the host-plant and included this in the photos

Grassland (limestone grassland in VC55)

Widespread, common (Redfern & Shirley 2023)

Rare.  Up to 2025, it has only been recorded from Ketton and Bloody Oaks quarries 

https://bladmineerders.nl/parasites/animalia/arthropoda/acari/actinotrichida/prostigmata/eleutherengona/eriophyoidea/eriophyidae/eriophyinae/acerini/aceria/aceria-thomasi/