There is a small man-made lake nearby that was drained to work on a dam (that blocks a creek that creates the lake). For two years, the lake was drained to rebuild the dam. Water was continuously pumped over the dam. The creek flowed through a muddy field that eventually was filled with plants. There weren’t a lot of dragonflies.
This past spring, the dam work was completed and the lake was allowed to fill. There seemed to be a large increase in dragonflies. In one small area, I easily found about 20 exoskeletons of various sizes one day in the plants surrounding the lake. When the lake was almost completely empty, I walked out to look at the plants from the other side. I found more exoskeletons. Unfortunately, the dam showed signs of cracks. So, the lake was drained again.
Did the eggs of the dragonflies lay dormant for those two years? Will that happen again if the repairs take a year or two to complete?