Illustration by EH Zeck.
This is an illustration of Grapeleaf blister mite Colomerus vitis (Pagenstecher) (Acari:Eriophyidae)
Order reference: grape-leaf-blister-mite
Blister mites, or felt mites, are so-called because they cause raised welts or felted areas on the leaves of their host plants. They are some of the smallest types of mites. The illustration shows areas of felted blisters on grape leaves which is a diagnostic symptom of the presence of blister mites. The mites themselves are microscopic, worm-shaped creatures with legs at one end. Zeck's illustration has captured the movement of the mites as they wriggle about on the leaf surface.