What Time is it in Nature: Blue Dasher Dragonflies Emerging
We have a lot of water here on the Prairie Ridge grounds. The stream and ponds are home to a variety of aquatic insects, including beetles, mayflies, caddisflies, and dragonflies. Even the little pond in the Nature Neighborhood Garden is teeming with life! Recently, an amazing biological spectacle has been taking place at the garden pond: the dragonflies are emerging.
Dragonflies begin their lives in water. After mating, female dragonflies typically deposit their eggs in water where they hatch and tiny nymphs emerge. Dragonflies are long-lived as nymphs, spending one to three years in the water hunting other insects, small fish, and tadpoles until they are ready to move onto land and become adults. This metamorphosis involves a complex series of steps, illustrated here by a series of photos of female Blue Dashers (Pachydiplax longipennis) as they make their amazing transformation from nymph to adult.
First, the nymphs crawl out of the water and make a slow, awkward climb up a piece of vegetation until they are a few inches above the water line. Once there, they swallow air and start puffing up their bodies until the exoskeleton cracks along the thorax and the dragonflies inside are able to start squeezing out through the hole:
Some other dragonfly species will use gravity to help pull their bodies out of the last nymphal exoskeleton by bending over backwards and pulling their body free upside down. The Blue Dashers free their heads, thoraxes, and legs and crawl up the stems to pull the rest of their body loose:
Once completely free, they begin to pump hemolymph (i.e. insect blood) into their wings and other body parts to stretch them out to their full size:
Dragonflies, like all other insects, are very vulnerable at this stage. The body inside the last nymphal exoskeleton is very soft and fragile and must be stretched and allowed time to harden before the insect can engage in its normal activities. So long as a dragonfly’s wings and body are soft, they cannot fly away if disturbed by a predator and they can be easily dislodged from their perches by a strong gust of wind. If all goes well, the wings will harden enough for the dragonflies to move them to their sides, the typical position of dragonfly wings when they’re at rest. The wings continue hardening and the body darkens:
For Blue Dasher females, this color is close to her final color, but males will continue to develop their color over several days. Eventually the newly emerged dragonfly will fly away, ready to begin its short life on land as an adult, hunting insects on the wing and looking for mates so that they can begin the whole cycle all over again.
The next time you visit Prairie Ridge, take a look in the garden pond in the Nature Neighborhood Garden or scan the vegetation along the banks of the pond. You just might be able to see this amazing transformation yourself!
What Time is it in Nature is a weekly feature highlighting the current plants, animals, and other wildlife at the Musuem’s public outdoor facility, Prairie Ridge Ecostation. Find out more about the natural happenings at Prairie Ridge at our What Time is it in Nature Archive!
(Photos by Chris Goforth)