Vail Curious Nature: Insects go through big changes
Vail, CO Colorado
VAIL VALLEY, Colorado –Every May, seventh grade students from Berry Creek and Eagle Valley middle schools conduct biodiversity research studies with Gore Range Natural Science School in Colorado’s Vail Valley.
Earlier this month, some students dressed in chest-high waders climbed into the frigid waters of Berry Creek in Edwards. As two students supported a three-foot square net, a third student kicked at the rocks, vegetation, and muck on the stream bottom. Upon pulling the net out of the water, students were introduced to a plethora of life from an underwater community that most of us do not often consider. The net was filled with a variety of insects, worms and other invertebrates.
Aquatic insects are an essential component of food chains in our streams and rivers. Insects that spend some or all of their lives in the water make up a portion of the diets of fish, birds and mammals.
Aquatic insects eat plants, detritus, food particles and even other aquatic insects. Fishermen keep close watch as to which insects the fish are eating and when different insects hatch and fly near the water.
Insects experience two kinds of life-process changes. Complete metamorphosis is the insect life cycle that most of us studied in elementary school by observing butterflies.
Metamorphosis means a change in form or development. In the complete metamorphosis life cycle, the adult female insect lays an egg and a worm-like creature called a larva hatches from the egg. Eventually, the larva builds a shelter called a pupa.
Inside the pupa, the insect changes form to become an adult insect. Finally, the insect emerges from the pupa as an adult. The adult insect and the larva of its youth do not resemble the other physically. The life cycle process will begin again when, after mating, a female adult lays its own eggs.
From the sample collected in Berry Creek, students identified two types of caddisfly larva, a cranefly larva and a couple beetle larvae. One day, all of these insects will leave the stream as adults to fly over the riparian community. Students also found a number of stonefly and mayfly nymphs. The nymph is a stage of the incomplete metamorphosis life cycle.
It can take a few weeks or up to a couple years for the entire incomplete metamorphosis life cycle to occur. In this life cycle, the adult female insect lays an egg. From the egg hatches a nymph. A nymph looks more like an adult insect than a larva does, but it is not yet an adult.
Insects that go through incomplete metamorphosis spend the majority of their lives as nymphs. As the nymph grows, it molts or sheds the exoskeleton and replaces it with a newer, larger version. When it is time to make the change to adulthood, a nymph emerges from the water, the nymph’s exoskeleton cracks open, and an adult insect crawls out.
When mayflies become adults, they have one mission and one day to complete it. Before it dies a mayfly must mate and lay eggs. Many species of mayflies do not have mouths as adults because they do not have the time or the need to eat.
As you walk near creeks and rivers this summer, turn over a rock to see if you can find any larvae or nymphs hidden there. Watch for an adult beetle swimming past you. Examine the tall grasses near the shore and perhaps you can find a stonefly exoskeleton that was left behind. Look at the insects flying around and say hello to the adult aquatic insects.
Lara Carlson is the Gore Range Natural Science School’s Avon in-school educator, where she leads students outdoors, educating them about Colorado creatures, big and small. (www.gorerange.org) The Gore Range Natural Science School’s Curious Nature column appears Mondays in the Vail Daily and on http://www.vaildaily.com.