Ken Tennessen
Wednesday, October 15, 2008 - 11:00-11:30
Approximately ten percent of the dragonflies (Insecta, Odonata) of the contiguous United States are rare enough to raise concerns about their continued existence. Most of these 45 species are rare because the habitats they require are naturally limited or have been drastically altered or eliminated. As for any group of organisms, conserving the proper habitat is the key in protecting dragonfly populations. In the United States, the most critical habitat types in need of protection for the aquatic immatures of rare dragonflies are sand/gravel streams, seeps, fens and small sandbottomed lakes. Also, the integrity of the ecosystems surrounding these aquatic habitats must be considered, as the aerial adults require shade and structure for feeding and finding mates. Evidence for the extent of global climate change on dragonflies is circumstantial; change in geographic ranges of certain species is being documented. However, data on change in distributions and populations of any Odonata species through time is scant. We frankly know very little about the nature of population increases and declines through successive generations. Monitoring by adult census is relatively difficult. Exuviae searching is a powerful tool now being used in more studies. However, methods for estimating populations based on quantitative exuviae collections are still being refined. Funding for such studies is a limiting factor.
Keywords: DRAGONFLIES, CRITICAL HABITAT, POPULATION MONITORING, EXUVIAE