The first pictures of the Riverine Clubtail (Stylurus amnicola) breaking through the skin was taken at 1:35 pm and I waited and continued taking pictures till it flew off at 3:00 pm. The whole process took 1 hour and 25 minutes.
The nymph picture was actually another that crawled out of the water at the same spot about an hour after the main subject one started eclosing. In all there were about 10 amnicola exuvia along a 200 yard stretch of the Connecticut River in Hatfield, Ma. Chris Gentes is helping on a clubtail survey on the river, and was kind enough to have me along. There were probably more, but after finding a live one we didn't go much further.