Found this clump of fluff a few days ago and initially wasn’t sure what it was. I’d assumed it was some sort of a gall, but when displayed on a big monitor I could see there were legs sticking out. Pretty sure it’s a spider parasitized by a cordyceps fungus. I’m guessing Torrubiella leiopus. But if I’m wrong about it being a spider underneath, I’ll retract that guess. Sort of looks like Sideshow Bob on The Simpsons.
Below are some photographs of strange adaxial growths on a patch of Asclepias syriaca at a preserve near me. There were perhaps 20 individuals that had variations on the growths, all on their the upper leaves. The milkweeds in the rest of the field all had normal leaves. Anyone seen this before?
From the few publications I’ve found, enations can be caused by viruses (Geminiviridae, Luteoviridae, etc.), and thus could be transmitted to nearby individuals via insect vectors or by the connected roots (milkweeds are clonal). Could be a genetic mutation, too, I suppose — could be spread by seed or via clonal growth.
Photographed at Hildacy Farm Preserve in Media, PA.