Persistence of dragonfly exuviae on vegetation and rock substrates

Surveys of dragonfly exuviae have been used to assess rare species' habitats, lake water quality status, and wetland restoration programs. Knowledge of the persistence of exuviae on various substrates is necessary to accurately interpret exuvial surveys. In 2006, we recorded exuvial persistence at defined areas in a variety of small freshwater wetlands in Rhode Island. Exuviae were field-identified, labeled with small daubs of nail polish, and observed every three weeks from June through September. Overall, exuvial persistence displayed exponential decline, disappearing rapidly during the first few weeks, and more slowly thereafter. The initial rate of decline was similar for most species, but differed in some taxa. There was no significant difference in exuvial retention on emergent vegetation vs. rock substrate.