Just as insects have evolved to fill numerous niches throughout the world, so, too, have they taken advantage of the Nebraska Sandhills. The diversity of habitats and landscapes across the Sandhills can be seen in the unique communities of insects found in these varied grasslands. Aquatic or semiaquatic insect communities are more common in the subirrigated meadows, and xeric or desert-loving species are more common on the dry dune tops. What makes the Sandhills unique is that these communities can change in a short 800-foot distance from the foot to the crest of a dune.
The habitats within the Sandhills to which insects have adapted can be surprising. Sand blowouts, while sometimes viewed negatively, are actually important habitat for several unique insect species. The sandy tiger beetle, Cincindela limbata, is specifically found in these habitats and stream banks nearly exclusively within the Sandhills. Other tiger beetle species also take advantage of these habitats, where they are key insect predators as adults and larvae. The complexity of coadaptation between species is remarkable within these systems. Insect decomposers, such as burying beetles and dung beetles, play crucial and diverse roles. While American burying beetles may work to decompose a prairie dog corpse, some dung beetle species have adapted to take advantage of prairie dog dung. These decomposers work in concert to restore nutrients to the soil to produce more grass that can then be consumed by herbivores. While habitat diversity over such short distances is impressive, the Sandhills ecoregion also varies at large scales. Longer growing seasons with more moisture are found to the east, with drier, shorter growing seasons to the west.
Insects take advantage of the plants that have adapted to the Sandhills’ diverse soil, water, and wind conditions. The yucca is an example of a plant that becomes more common as you move from east to west across the Sandhills. And it provides an example of the diversity and unique adaptation of Sandhills insects. Four yucca species are common to Nebraska: Yucca glauca, Y. aloifolia, Y. recurvifolia, and Y. filamentosa. Although high densities of these plants can be problematic for ranchers, they do support an interesting and diverse insect life. Several species of insects thrive on yucca. Giant skipper butterflies feed on the stems as caterpillars and pollinate the flowers as adults. Meanwhile, Cole’s bush cicadas (Megatibicen tremulus) call for mates on yucca stalks, and the female lays her eggs on the plant. The nymphs then live out their lives underground, feeding on sap from the yucca root. This cicada is particularly interesting as the species is referred to as a “cryptic” species, meaning M. tremulus looks exactly like another cicada, Tibicen dorsatus.
Researchers were able to identify the species as separate when they analyzed their distinctive calls.
Although much attention has been given to insects as pests, only a small number have negative economic or societal impacts. The majority of insects serve critical roles, providing ecosystem services from decomposition to pollination.
Grasshoppers have a notorious reputation in Nebraska and throughout western rangelands for competing with cattle for grass. Indeed, there are three to five species of grasshopper common to grasslands that are commonly referred to as “outbreak species.” Climatic and environmental cycles can lead to very high densities of some grasshoppers and when combined with drought can be very destructive to rangeland if left unmanaged. However, there are around a hundred species of grasshoppers that are common to Nebraska. Similar to insect species overall, most grasshoppers are not pests. In fact, Russian thistle grasshopper (Aeoloplides turnbulli) might be considered beneficial as it feeds on Russian thistle and lambsquarters, while snakeweed grasshopper (Hesperotettix viridis) preferentially feeds on snakeweeds, which are toxic to cattle. Some species of grasshopper, such as painted grasshopper (Dactylotum bicolor), have a striking appearance and specific hosts preferences.
Insects in the Sandhills can also serve as a food source for other animals. The clean, clear ephemeral ponds and streams in the Sandhills can support extremely high populations of mayflies (Ephemeroptera) for example. Immature mayflies (nymphs) feed off algae and detritus along the stream or pond bottom. Mayflies may live up to two years in this immature, aquatic stage. However, adults might only live a day or two following emergence from their aquatic stage, primarily in the spring. Mayfly hatches can reach very high densities and are weak flyers; bats, birds, amphibians, and fish all take advantage of the adults as food sources.
Cutworm species (Noctuidae) overwinter in Sandhills soils and some, such as the army cutworm (Euxoa auxillaris), can reach very high densities on Nebraska grasslands. While outbreak populations can denude large areas of grass, many ground-nesting birds depend on foraging for cutworms in the spring as they provide the protein needed to support egg production and nesting chicks. The surviving caterpillars of the army cutworm become a moth that migrates west in late spring to early summer and will oversummer high in the Rocky Mountains. These moths become critical protein sources for grizzly bears as they forage among the scree fields in the high mountains. It’s interesting to reflect on the impact of the Sandhills ecosystems even across the continent.
Insects are the most species-rich group of animals on Earth. Their size, mobility, and life strategies have afforded them the ability to adapt to nearly every terrestrial and freshwater niche on the planet. The precise number of insect species is a topic for some debate—there could be as many as thirty million insect species—yet only about nine hundred thousand living species have been described.
Nebraska’s Sandhills represent an ecoregion ripe for research into the roles and numbers of insect inhabitants. The overwhelming number of insect species has yet to be studied sufficiently to fully understand their roles within ecosystems. This is especially true for unique, hard-to-find species, many of which can be found in the Nebraska Sandhills. They provide important ecosystem services in their aesthetic beauty, maintaining natural cycles that pollinate flowers, recycling nutrients back into the soil, and providing food for other wildlife in Nebraska ecosystems and beyond.