Very slight near-circular swellings of the lamina of Quercus agrifolia with a very slight papilla in the center on the lower side. Sometimes seen in numbers, overlapping to form larger blotches. Initially green, fading to a nearly-white tan.

Observed on Quercus agrifolia in California in May (2) and observed on Q. kelloggii in late April.

Very tentatively treated here and on iNaturalist, as genus Polystepha, a genus that causes blister or pill-like leaf galls. In North America, Polystepha galls have been found exclusively on red and black oaks. Eiseman observes, in "Miscellaneous Records of Cecidomyiidae (Diptera) from the USA," Proceedings of the Entomological Society of Washington 126(4), 454-473, (21 April 2025), page 464, that "As far as is known, Polystepha spp. are the only cecidomyiids that cause leaf spot and blister galls on oaks."

- Gallformers Contributors: (2024) Gallformers ID Notes^©