In many parts of the country, we’re starting to see mosquitoes, especially after heavy rains. Mosquitoes love brackish pools, but so do gators and crocodiles, which mate this time of year…and dragonflies. Over Memorial Day weekend, I delighted in watching an army of dragonflies zip around me at killer speeds. They eat mosquitoes. So it begs the question, do more mosquitoes mean more dragonflies? If so, that would be good news for people heading outside to enjoy the warm weather. So far I’ve only had to wear my DDT-free bug spray once on a walk along the pond.
A recent New York Times article provided news about endangered species (A Coast-to-Coast Guide to Endangered Species) including the bog turtle, ringed boghaunter and the orange-striped dragonfly, which were described as some of the rarest wetland-dwelling species in the U.S. For an amazing montage of rare photos 
taken at the Texan Cibilo Nature Center of the orange-striped dragonfly in courtship, see: http://www.martinreid.com/
Odonata%20website/odonate37b.html
Dragonflies are generally known as freshwater insects. But recent research has demonstrated that dragonflies are no strangers to brackish environments. What is brackish water? Brackish pools, sometimes called brackish marshes, are saltier (more saline) than freshwater but not as salty as seawater. Typically brackish water occurs where the sea meets freshwater—estuaries, mangroves and saltmarshes. Many species of fish depend on these waters for their migration from the sea to rivers and streams, such as eels and salmon. In addition there are also brackish lakes, e.g. Lake Monroe in Florida and Lake Charles in Louisiana. For a photo of a dragonfly’s exoskeleton at Lake Charles, see http://www.flickr.com/photos/atweed/4651677110/
A relatively recent issue of Canadian Field Naturalist featured an article by Paul Catling on “Dragonflies Emerging from Brackish Pools of Saltmarshes in Quebec” (CAN), citing his research that showed dragonflies used salt marshes much more often than had been previously understood. For an example of a brackish pool in a saltmarsh, see http://www.sciencephoto.com/media/
175707/view The importance of brackish pools as habitat for young dragonflies, called nymphs, has long been observed by naturalists, as noted by Raymond Osburn (The American Naturalist,1906 http://www.jstor.org/pss/2455367) Catling’s research has shown, a century later, that dragonflies do in fact utilize saltmarshes, which contain an abundance of estuarine and marine life. Either dragonflies have evolved to move into saltmarshes or earlier observations by naturalists have left that distinction out of literature.
One contemporary naturalist photographed a Tawny Pennant (Brachymesia herbida) in a saltmarsh in the Bosa Chica tract of a National Wildlife Refuge in Brownsville, TX http://www.duke.edu/~jsr6/Brachyherb.jpg Here’s a dragonfly in a saltmarsh of Daufin Island, AL http://www.flickr.com/photos/littoraria/3639808921/ But a simple Google Images search will reveal that it is rare to find photos of adult dragonflies in saltmarshes. This may be due in part to the challenges of wildlife photography, especially with respect to 
capturing a fast-moving target, such as a dragonfly, on film. The best advice from our own Compleat Wetlander’s nature photographer, Jeanne Christie: “Wait for the wildlife to come to you.”
Bonus activity for kids: How to draw a dragonfly. http://www.how-to-draw-cartoons-online.com/dragonfly-drawings.html
Updated April 2013: Dragonflies Drive Dedicated Fans to Refuges
http://www.fws.gov/news/blog/index.cfm/2013/4/2/Dragonflies-Drive-Dedicated-Fans-to-Refuges
In 1959, I worked as a medical entomologist for the State of So. Carolina. While meeting with a large land owner in the coastal area, we noted a large dragonfly (mosquito hawk) hatch eliminating a hatch of salt marsh (Aedes) mosquitoes. The plantation owner and I discussed what happened. I explained that this was a fortunate occurrence, but of relatively short duration.
He offered to pay for a master’s degree at Clemson University and use of plantation lands and any equipment needed for dragonfly production. While I roughed out a methodology for dragonfly production, I could not come up with a reasonable way to produce large enough numbers ccntinuously to be effective.