"Trout Run Trail, Decorah, Winneshiek County, Iowa, USA; May 10, 2014; Size: ~2mm: I came upon a variety of birds gobbling up something from the paved surface of a bike trail in Decorah, beneath the canopy of an elm tree (American elm, I believe). It took me a while to figure out the trail under the elm was littered with these tiny grubs, which seemed to be falling out of the tree. Further investigation revealed that many of the developing samaras on the tree hosted small galls -- more or less cone-shaped with an opening on the tapered end. As I recall I actually noticed one of these grubs emerging from a gall on a samara. There were plenty of birds feasting on the ground (see species list below) but a number of warblers were in the tree itself as well, foraging among the clusters of samaras, seemingly grabbing and tugging at individual samaras as if extricating the grubs from them (or grabbing them as they emerged from their galls)...Didn't quantify this but it seemed many of the infested samaras had shriveled / underdeveloped seeds...I dissected several such infested samaras, and discovered that the gall was its own chamber, separate from the space within the samara where the developing seed was located." - John van der Linden, notes from several observations published on Bugguide.