Aquatic Insects, Harbingers of Health

Aquatic Insects, Harbingers of Health
Skwala (Large Springflies)
Stonefly Nymph
Courtesy & Copyright
Robert Newell
As found on

Aquatic Insects, Harbingers of HealthMayfly nymph
Courtesy & Copyright
Leo Kenney, Vernal Pool Association

Aquatic Insects, Harbingers of HealthNorthern caddisfly Larvae

Photo Credit:
Howard Ensign Evans,
Colorado State University,
Used under
Creative Commons Attribution 3.0

Hi, this is Mark Larese-Casanova from the Utah Master Naturalist Program at Utah State University Extension.

As we officially enter summer, it’s easy to notice nature at its peak. Wildflowers are in bloom, birds are feeding their young, and insects fill the air. Life is especially robust near our wetlands, lakes, and streams.

Our aquatic, or wet, ecosystems provide habitat to abundant plants and animals. Only 1% of Utah is wet, but over 80% of all wildlife in Utah depend on aquatic ecosystems for at least part of their life cycle. However, the quality of Utah’s aquatic habitats is often affected by chemical pollution or excessive nutrients and sediment.

Some organisms, including many aquatic insects, only live in the healthiest of aquatic habitats. Many of the insects we see in summer live in the water when young, during the larval or nymph stage, before becoming adults. Three insects in particular- mayflies, stoneflies, and caddisflies- require especially clean, cold streams low in nutrients and high in dissolved oxygen to survive.

Mayflies are aquatic as nymphs and emerge from the water to live as adults for just a day. The external feather-like gills of the nymphs can be seen fluttering along the sides of their abdomen. They feed by scraping algae from rocks.

Stonefly nymphs are well adapted to living among the rocks of swift-moving streams. Their hooked legs grasp the slick rocks as they shred apart plant litter that falls into the stream.

Caddisfly larvae spin a sort of spider silk to glue rocks or sticks together to form a case in which they live. They will also build webs underwater to collect small particles of food that drift by.

The quality of a stream habitat can be assessed by counting the number of different species, or types, of mayflies, stoneflies, and caddisflies. A greater number of species generally means that habitat and water quality are higher. Dramatic decreases in insect diversity from season to season or year to year can signal a decline in stream health. Monitoring aquatic insects over time gives us an accurate picture of the long-term health of our stream ecosystems.

For more information about monitoring water quality and aquatic insects, visit Utah State University Water Quality Extension’s website. Once there, you’ll find a wealth of information about monitoring Utah’s aquatic ecosystems, including Utah Water Watch, a statewide volunteer citizen science program.

For Wild About Utah, I’m Mark Larese-Casanova.

Images: Northern caddisfly larvae, Howard Ensign Evans,
            Colorado State University
            Creative Commons Attribution 3.0 License.
            Stonefly Nymph, © Robert Newell, displayed on
            Mayfly nymph, © Leo Kenney Vernal Pool Association
Text:     Mark Larese-Casanova, Utah Master Naturalist Program
            at Utah State University Extension.

Additional Reading:

Larese-Casanova, M. Utah Master Naturalist Watersheds Wildlife Field Guide. Utah State University Extension. 2012.

USU Water Quality Extension. Utah Stream Team Manual.

Voshell, J. R. A Guide to Common Freshwater Invertebrates of North America. The McDonald and Woddward Publishing Company. 2002.

Fossil Formation

Fossilized fish
Mioplosus labracoides
Copyright 2013 Stokes Nature Center
Andrea Liberatore, Photographer

Fossilized fish
Copyright 2013 Stokes Nature Center
Andrea Liberatore, Photographer

Horn Corals from Logan Canyon
Copyright 2013 Stokes Nature Center
Andrea Liberatore, Photographer

Fossilized leaf
Copyright 2013 Stokes Nature Center
Andrea Liberatore, Photographer

Fossilized shells
Copyright 2013 Stokes Nature Center
Andrea Liberatore, Photographer

The most popular school program that the Stokes Nature Center offers is a geology lesson for second grade. I’m not sure what happens between second grade and adulthood to make our general perception of geology go from exciting to boring, but you would be amazed at how excited second graders get over rocks, and especially, over fossils.

Fossils are really quite rare – a very specific set of conditions have to be met in order to create one. Most living things decompose fairly rapidly upon death, leaving no trace of their existence behind. In order to create a fossil, this process of decomposition needs to be halted fairly rapidly, which typically means that the body is quickly covered by some kind of sediment – like sand, or soil or mud. For this reason, most fossils are found embedded in sedimentary rock. If pressure and moisture levels are just right, over the course of millions of years the organism’s molecules will slowly be replaced by minerals from the surrounding sediments – eventually turning bone into stone.

Only somewhere around one in a billion bones will make it through this process. From there the fossil has to remain intact and identifiable through eons of tectonic plate movement, earthquakes, and mountain uplift. Then, in order to be found it has to be located near enough to the earth’s surface, and in such a place where a human might come across it. Some geologists estimate that only 1 in 10,000 species that have ever lived have made it into the known fossil record, which makes me wonder what discoveries still await us.

Fortunately for us, prehistoric Utah was a place where fossilization happened with some regularity, as evidenced by places like Dinosaur National Monument and the Escalante Petrified Forest. Did you know that Utah has a state fossil? That distinction goes to the allosaurus, a predatory dinosaur that thrived during the Late Jurassic period. Numerous skeletons found in east-central Utah range in size from 10 – 40 feet in length, meaning this fearsome creature may have rivaled it’s more famous cousin Tyrannosaurus Rex for top predator status.

With such a rich fossil history, it’s not out of the question that you might stumble onto something truly amazing during a routine hike. Can you keep your find? Well, that depends on two things: the type of fossil, and whose land it was found on. On public lands in Utah, fossils of vertebrates cannot be collected, while fossils of invertebrates and plants can be. Private land owners have full rights to the fossils found on their property. With all fossils, it’s a great idea to report your find to the US Geological Survey so that your discovery can be documented for public or scientific research, display or education.

Fossil creation is an incredible phenomenon that has allowed us to glimpse the earth’s history in ways that would otherwise be completely hidden. Thanks to fossils, we can envision a prehistoric landscape filled with giant ferns, enormous dragonflies, long-necked allosauruses, and flying pterodactyls. Without the evidence in the fossil record, I doubt that even the most imaginative person among us could have envisioned such an amazing array of life.

For the Stokes Nature Center and Wild About Utah, this is Andrea Liberatore.


Photos: Courtesy & © Stokes Nature Center,
Text:    Andrea Liberatore, Stokes Nature Center,

Additional Reading:

State of Utah, Utah Geological Survey, Dinosaurs & Fossils (2011)

McCalla, Carole and Eldredge, Sandy (2009) What should you do if you find a fossil? Utah Geological Survey. Accessible online at:

Trefil, James (1996) 101 Things You Don’t Know About Science and Nobody Else Does Either. Houghton Mifflin Company: New York, NY,

Bryson, Bill (2003) A Short History of Nearly Everything. Broadway Books. New York, NY,