I think I’m safe in saying that not many, if any of my readers spend as much of their time staring at, turning over, or fossicking among leaves as I do. So, you may not have noticed that, at this time of year, many of the leaves on Blackthorn (or Sloe) trees (Prunus spinosa) develop lots of little lumps and bumps.

These are galls, caused by the tiny mites Eriophyes similis. My Field Studies Council guide to galls explains that ‘mites are small enough to pierce and feed on individual plant cells, and by so doing to cause surrounding cells to enlarge and multiply.’ The galls start out green and gradually turn a pinkish colour., as shown in my photos, and are often found around the edges of the leaves. This mite species appears to have had a recent change of name, as many older publications label them as Eriophyes spinosae.