ecology

     Insects of the
Great Salt Lake Playa

What species can be found around the Great Salt Lake?

     Three of the most common insect groups found on the Great Salt Lake Playa and their margins are the spiders, the grasshoppers and the tiger beetles. These insects are important to the maintenance of the Great Salt Lake playa ecosystem as they are prey for nesting birds as well as migrating shore birds. Some of these predatory insects feast on other abundant insects found around the lake shore. Spiders What Spiders will you see around the lake?
Where will you be able to see them?
How are spiders important in the Great Salt Lake Playa food web?

What Spiders will you see around the lake?

         One of the most common families of arachnids found around the lake is the Araneidae, or the common Orb Weaver. This species typically spins snares in the form of an orb, or circular web, to catch its prey.
The Common Orb Weaver.

Where will you be able to see them?

These spiders are usually found in the less alkaline areas all around the lake where the common vegetation is grass and shrubs. In addition, they can be found at the GSL Marina on the lake's south shore between the rocks and often in or on the boats. In fact, in the early 90's, there was an outbreak of orb weavers at the marina because the abundance of nutrients, particularly brine flies, was so great. This increase in brine fly reproduction may have been due to several factors like a decrease in the salinity in the south arm of the lake, which occurred in the late 1980s and early 90s. This fluctuation in salinity levels may have resulted in an increase in the growth of certain algal species, like the Dunaliellia, which is the main food source for the brine fly.

How are spiders important in the GSL Playa food web?

The spiders of the Great Salt Lake playa and lake shores are prey for the thousands of birds that migrate through the area each year including the snowy ploverand the American avocet. In addition, they are also a main source of food for the savannah sparrow which is common in the grassy areas year around. Insects, like the spider, are a source of calcium for the birds. These spiders are attracted to the area because they feast on the hundreds of millions of adult brine flies that swarm on and around the lake. In the natural ecology of the area, if there is an outbreak of brine flies, there will also be an outbreak of spiders because of the great abundance of food. Also, the more spiders and brine flies living in the area, the more migratory birds will be found there because of the additional food.
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Grasshoppers

What species will you see around the lake?
Where will you find them?
How do they contribute to the GSL ecosystem?

What species will you see around the lake?

The most common species of the Acrididae (grasshopper) family around the Great Salt Lake are of the Melanoplus genus, like Melanoplus differentialis or Melanoplus femur-rubrum. In addition, another species found near the playa is the anabrus simplex, commonly called the Mormon cricket even though it isn't part of the cricket family. These species are very important ecololgically in that they are migratory and have weather dependent population cycles. They have the ability to destroy entire crops in one sweeping wave. The differential grasshopper has the ability to hop and fly hundreds of miles in search of food and a warm climate while the Mormon cricket is wingless and travels in a slow moving wave of brown.
For example, in 1848, hordes of Mormon crickets invaded Utah fields, threatening to destroy all of the crops in their path. Flocks of seagulls came seemingly magically from the heavens after intense prayers to devoured all of the insects, saving the crops for the pioneers. The Mormon pioneers erected a monument to tme "miracle of the gulls" to commemorate the event and they are now protected as the state bird. In addition, the differential grasshopper completely devestated the crops of the Great Plains region a generation ago, leaving only barren fields and hopeless farmers behind.
Image taken from reference 4.

Anabrus simplex Melanoplus differentialis

Where will you find them?

As you would expect, because the grasshoppers eat mainly green grasses, you expect to find them in the saline plains community, a couple of feet in elevation above the saltgrass zone and also in the higher desert elevations where sage brush and grasses are common. Plants typical of the the saline plains are the tall greasewood shrub (Sarcobatus vermiculatus), the shorter shadscale shrubs (Atriplex confertifolia), alkali dropseed (sporobolus airoides), and green weeds like wild barley, peppergrass, and the incessant cheat grass. The insects tend to frequent these areas because there is nutritious green food available and also they can easily hide in the dense shrubs. They also prefer these drier areas because they deposit their eggs into burrows in the ground for hatching in the spring.

How do they contribute to the GSL ecosystem?

The grasshoppers play an important role in the ecosystem of the Great Salt Lake Playa community, both in what it eats and in what eats it. Grasshoppers control the amount of food available for other species of insects and also the habitat for the mammals that live on the playa by what and how much they eat. If there is an overpopulation of this species, they can consume grasses and affect seed production in subsequent years. This, in turn, reduces the food supply for species like the Savannah sparrow and the vole who survive on the seeds and this also disturbs their living habitat. Those species like the northern harrier,snowy plover and seagull which prey on the various grasshopper species require the protein and calcium that they provide. Because grasshoppers are an alternative source of food for many different kinds of birds throughout the year, the young, newly hatched grasshoppers may be important for newly hatched plover, curlews, and savannah sparrow which nest on and around the playa. Later on in the summer when the grasshoppers are larger adults, they are an important source of nutrients for harrier hawks, seagulls, and other shore birds.

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Tigerbeetle

What species will you find?
Where will you find them?
How do they fit into the GSL food web?

What species will you find?

In North America, there are five common species of tigerbeetle found in alkaline areas like that of the Great Salt Lake Playa. These species prefer this type of area because the humidity, light intensity and temperature, about 15 degrees celsius, are optimal. The physical characteristics that make the tigerbeetle suited to the playa are its camoflauged exoskeleton and short, fast flying. The bright colors and markings on the backs of the beetle serve as a protective mechanism against predators like the dragonfly by making it virtually unrecognizable against the background. Image taken from reference 4.

Adult Tigerbeetle

Although we are not sure which species are abundantly found on the GSL playa, some possibile species are C. willistoni, C. nevadica, C. togata, C. circumpicta and C. marginata. Generally, the tigerbeetle will stay about two to three feet in front of any moving threat so they are very difficult to catch and even more difficult to see closely. One of the unique protective behaviors of the larvae is that they burrow themselves into the ground where they stay just near enough to the surface to snatch up any prey that may be unfortunate enough to pass over the hole. Also, adults will bury themselves under the soil to escape predators and also unfavorable weather, hot and dry or cold and wet. Tigerbeetles hibernating beneath the soil during the cold winter months and emerge with warmer conditions in the
Spring.

Tigerbeetle larvae beneath the soil.

Where will you find them?

Great Salt Lake tigerbeetles are commonly found all over the flat, bare, salty playas. They tend to frequent these areas more than the pickleweed zone because they require bare, dry soil to burrow in and also because they can tolerate the moderate salinity of the salt crust.

Habitat typical of the tigerbeetle.

How do they fit into the GSL food web?

Despite their many protective behaviors, the tigerbeetle may fail to escape being prey for other, larger species of insects, mammals and birds. It has been noted that large dragonflies feast on the tiger beetle, as do migratory birds like the American avocet and the snowy plover. Surprisingly, other carnivorous mammals like the badger and fox eat them, as well. Unfortunately, the greatest predator to the tigerbeetle is the human and the off-road vehicle. These two things tend to disturb both the soil and habitat, thereby killing many pupae, larvae and adults. (As mentioned above, the tigerbeetle feeds on smaller insects like ants and other arthopods.) [back to main page]

References:
1. Dunn, Gary. 1998. Tiger Beetle World. http://members.aol.com/YESedu/home.html (20 Nov. 1999)

2. Johnson and Rawley. 1974. The Great Salt Lake Population Ecology. Utah Dept. of Natural Resources. 74-13.

3. Kaston, B.J. 1978. How to know the spiders, third edition. WCB/McGraw-Hill, Boston, MA, USA.

4. Little, V.A. 1963. General and Applied Entomology. Harper and Row, New York, NY, USA.

5. Nieuwenhuys, Ed. 1998. Argiopes from the USA. http://www.xs4all.nl/~ednieuw/Spiders/ArgiopesUS/Argiopes_USA.html (20 Nov. 1999)

6. Rawley, E. 1980. Great Salt Lake: A scientific, historical and economic overview. Utah Dept. of Natural Resources. 116.

7. Spangler, J. 1991. "Spiders flock to marina at Great Salt Lake for feasts of brine flies". Deseret News. Salt Lake City, UT.

8. Wardle, R.A. 1936. General Entomolgy. Maple Press Co, York, PA, USA.

9. Wharton, T. 1992. "Flies draw shore birds to Great Salt Lake". Salt Lake Tribune. C8.

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