Eriophyidae

The Eriophyidae or gall mites are a family of mites. They are plant parasites and produce galls.
The mites can cause severe damage to the host plant. They have only two pairs of legs and are very small, 0.08 mm - 0.3 mm. The gut is straight, there are no outgrowths of the gut. They have no heart or circulatory system.
Some genera.
There about 270 genera and over 3000 species.
Some examples: