Here the eggs are hatching and the larva are dispersing.
Cf. the structure housing the eggs.
https://www.inaturalist.org/observations/67698787
After historically planted American Ash were cut down in the Sanctuary, a massive seed bank created a seedling forest. Pic 2 shows removal by tree popper. Fortunately, the grassland has rehabilitated.
Pic 1 is a coppiced stump. These trees grow readily in wet/marshy conditions.