DESCRIPTION: The gall mite, in this instance, is responsible for the small rounded growths that appear on the leaves of the host plant.  The galls are hard walled, are between 2 to 4mm across and have an inner surface that is coated with multi-celled hairs.  The galls are often found in the angles between the leaf veins.  DISTRIBUTION: Widespread. Best seen during the summer months from mid-June onwards. HABITAT: On the leaves of Field Maple.