Written by Bronwyn Earthman, Naturalist, Kroening Nature Center
Next time you find yourself near a pond or wetland, get down low and take a closer look at what is swimming around in the shallows. So often, we find ourselves paying attention to the easier to spot birds and butterflies that flutter around the prairie or skim along the surface of the water, and we forget to look closely at the vast and busy world that lies beneath the surface. Most of the creatures you might see swimming around are likely macroinvertebrates, a word that just means an animal you can see with the naked eye that does not have a spine. A dragonfly larva, for example, is an invertebrate, as are all insects, while tadpoles are vertebrates, like us!
Dragonfly larvae, or “nymphs” come in many different sizes depending on the stage of growth and species, however they have been known to grow up to 2.3 inches long. The nymphs continue to molt as they grow bigger and bigger, generally molting between five and 15 times throughout their aquatic lives, until eventually they are ready to emerge on the surface with newly grown wings, ready to fly around above the water in their adult form. Dragonflies are voracious predators in both their nymphal and adult stages. Dragonfly nymphs will eat other aquatic invertebrates, and the larger nymphs are even known to eat tadpoles and small fish! The adults make good use of their excellent eyesight and their highly controlled flight skills to capture flying insects.
You might also see damselfly larvae, which are smaller and more dainty versions of dragonflies in their adult form, as well as in their larval form. They have three appendages at the end of their bodies that look like tails, however these are actually external gills used for breathing. Like dragonflies, the nymphs molt about 12 times as they grow larger, until they too emerge from the water and molt a final time as their wings emerge. On a cool day, this process of emerging can take up to two hours, but on a hot sunny day, their exoskeleton hardens faster, and the damselfly can take up flight within half an hour.
The abundance of certain aquatic macroinvertebrates can be a great indicator of water quality. Dragonflies and damselflies are both relatively sensitive to polluted water, so if you are seeing lots of them zipping around, either in the air or in the water, that is a great sign that the water is likely relatively healthy! There are other species that are much more tolerant to pollution, such as leeches, midge larvae and certain kinds of snails. If you were to find more leeches and orb snails than anything else, for example, that might be an indicator that the body of water might be in trouble. So, look close next time you are enjoying a pond, wetland, creek or other body of water, see what kinds of creatures you can find, and what they can tell you about the health of the ecosystem!
Come visit the nature center for one of our upcoming July programs:
Nature Tots: Bee Friendly · Saturday July 6, 10:30-11:30 a.m. |Free |Ages 2-5 with an adult| Activity #6452|. Make a six-legged friend this summer! Explore the life cycle of a bee. Go outside for an up-close look at the busy bees in our prairie and learn how to ‘bee’ friendly with these helpful neighbors. This is an adult/child interactive experience.
Family Fundays: Wildflowers · Saturday July 13, 10:30 a.m.-noon |Free| All Ages| Activity #6467|. Why do flowers look the way they do? Join a naturalist to look for different types of flowers in our prairie, learn about how flowers and pollinators interact, and make a floral craft.
Nature Art: Art in the Landscape: Forest Fairy Houses · Saturday July 20, 1:30-2:30 p.m. |Free |All Ages| Activity #6487|. Are there fairies in the forest? Use your imagination and natural materials to build a home to leave in the woods for our local fairies and woodland friends.
Summer Birding · Saturday July 27, 9-10:30 a.m. |$5/person | Ages 18+| Activity #9954 |. Learn distinguishing characteristics of birds found in the park, including plumage, bird songs and calls, and behavior, while strolling with a naturalist through the park. All experience levels welcome.
Adventure Hub Highlight: Prairie Exploration · Saturday July 27, 1-2 p.m. | Free | All Ages | Activity #6484 |. Go on a walk with a naturalist to observe the flowers and insects in the prairie, then check out an Adventure Hub kit to explore the prairie on your own.