I don't think I collected these, but I know roughly where I saw them, so I could try to go back and find them. When do you think might be the best time of year to collect them if I find them in a future year? If collecting them at this time of year could yield something, I can go back and see what I can find...

Hi Tracy, if these are indeed wasp galls, the ideal time is now! Cynipid galls on herbaceous plants can be collected from late fall through early summer (essentially, any time after the first frost of the year but before the emergence time for that specific gall). It would be fantastic to know if these are still present at that site. Feel free to email me if you'd be interested in discussing further - lfnastasi@gmail.com

I'll see what I can do. I realized that the site I am most familiar with is one I have been visiting since 2019. I went with Bruce Sorrie (who led the way), and so I am not sure if I'd be able to find that site again. The host plant is S. compositum rather than S. laciniatum, actually. I know of other sites where the plant is common, so I can try to look there at least. I will also try to figure out where the original site is.

S. compositum is a species not yet known to host gall wasps but it is certainly a possible host. Cynipid galls are formally recorded from only 4 Silphium species in the midwest but I have material reared from a number of other hosts. Silphium can have galls on the terminal stems, in the flowers, on the lower stems, and hidden galls concealed entirely within the stems. It's an exceptionally interesting system - if you wouldn't mind doing some investigating, it's likely that galls on S. compositum are all undescribed species unknown to science, and I'd be greatly interested in determining whether this is the case.

Sure--I'll definitely keep my eyes open. I will try to get back to the site I have visited since 2019 at least. I've mostly been working on leaf-mining insects, and have found several new species on different plants across NC. So I do get around, and I'll be on the lookout. I also see a lot of Silphium asteriscus in the Durham area, but have seen no galls that I can recall yet. I will let you know if I find something.

Brilliant, thank you! Thus far we have found cryptic, imperceptible galls in the stems of Silphium dentatum and S. trifoliatum, both of which are variously treated as varieties of S. asteriscus - there might certainly be galls in your area!