Pachypsylla celtidisumbilicus n. sp.

This gall occurs on the upper side of the leaf, is regularly circular in outline and abruptly depressed at its outer margin beneath the surface of the leaf. From this outer margin toward the center the gall gradually rises again to about the level of the surface or even above it, the center being furnished with an elongate nipple (frequently broken off). The color in fresh specimens is a little lighter than that of the leaf, but fully developed and dried specimens are more yellow. Surface opaque, either without any decided sculpture, or rugose and with the venation of the leaf still preserved. On the under side of the leaf it is distinctly elevated, averaging 2 mm in height and 5 mm wide, circular in outline, the sides not abruptly elevated but gradually rising, with a larger or smaller shallow depression at top which is often furnished with a small central nipple. Color, yellowish-green in fresh, and more yellow in dried specimens ; surface opaque, rugose. Gall woody and hard, the wall at the bottom about 1 mm in thickness; that of the roof about 0.5 mm. Cell formed as in the preceding species [Pachypsylla celtidisvesicula], but much larger; mode of issuing of mature pupa also as in the preceding. There is no difficulty in recognizing this gall, especially from its appearance on the upper side of a leaf.

- CV Riley: (1890) Insects injurious to the hackberry^©

Reference: https://www.biodiversitylibrary.org/item/42358#page/633/mode/1up