I’d like to invite those of you who are interested to go look for galls on hickory leaves. There are 44 phylloxera and 62 cecidomyiid midge species known to make galls on hickories in North America; iNat has 12 and ~40 reported respectively, with most represented by only a few observations. Comprehensive descriptions have been made for both groups and I’ve put together a searchable version of the midge gall key here: https://www.inaturalist.org/guides/12068
Compared to other gall-forming groups, hickory midge galls are extremely underreported because they’re very small and rarely apparent unless you look under the leaf. But if you know to look for them they’re very cool-looking and extremely abundant, especially in areas where hickories occur in clumps. I found 14(!) species of them today in an hour or so of searching in the first place I looked.
Most species are widely distributed in the eastern US but one (which we’re missing) is endemic to Florida (underside of Carya floridana leaves) so bonus points for finding that one.
If you do find some, try to document:
– the host hickory species or its identifying characters (number of leaflets per stem, presence/absence of pubescence on the lower leaf and along the leaf edge)
– the gall’s internal structure
– the top and bottom of the leaf where the gall is attached