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Invertebrates

Anything But Creepy and Crawly
Spiders

Many species of insects occur throughout all habitats in the Monument. The diversity of insect life on the Monument is very high—over 1,500 species have been documented. Because of their extraordinary diversity and intimate interactions with vegetation, insects are one of the most sensitive measures of ecosystem quality and function.

The Hanford Site likely represents the closest approximation to a pre-European colonization insect fauna as can be found in eastern Washington. The diverse insect fauna of the Monument was one of the resources called out in the Presidential Proclamation establishing the Monument. The source of the Monument’s insect diversity and unique character can be attributed to the size, diversity and relatively undisturbed condition of its native vegetation and other natural habitat characteristics. For example, several groups of insects appear to be associated with areas of extensive microbiotic soil crusts; mite and Collembola (springtail) fauna are abundant where the crust is intact and are virtually nonexistent where the crust has been destroyed, which is most of the state.

Most insects are associated with specific microhabitats or host plants, are short-lived, and travel only short distances during their life. Unlike birds and mammals that may colonize an area if suitable habitat develops, the ability of insects to re-invade sites is minimal. Preservation of the variety of habitats available throughout the Monument is therefore particularly important for invertebrate conservation.

Darkling beetles are some of the more conspicuous ground-dwelling insects on the Hanford Site, including the Monument. These beetles play an important role in the nutrient cycling in shrub-steppe communities and are prey for a variety of mammals. Darkling beetles are generally more abundant in warmer and drier locations and in areas dominated by native vegetation, and thus may be a good indicator of change in shrub-steppe habitats.

The Rattlesnake Unit, including the Arid Lands Ecology Reserve, is particularly rich in butterflies and moths; 46 butterfly species and 107 moth taxa have been identified. Umtanum Ridge, Rattlesnake Ridge, and the shorelines of the Columbia River appear to support a wide variety of butterflies, including several rare species. An alkaline spring on Umtanum Ridge supports an endemic snail not described anywhere else in the world.

Aquatic insects, which are a critical link in the ecosystem and support the healthy fall chinook population, as well as the native resident fish community, include 145 taxa on the Hanford Site.

If you're interested in the extensive insect study, read on.

By the way, 'lepidopterans' are people who study butterflies and moths.

In 1994 and 1995, terrestrial invertebrate inventories were conducted, concentrating on particular insect groups, including leafhoppers and their relatives, true bugs, beetles, bees and wasps, true flies, and butterflies and moths. During 1996 and 1997, inventory efforts concentrated on moths and other night-active insects attracted to light traps and on butterflies. Surveys in 1998 broadened the sampling methods to include pitfall traps. These five years of insect inventory work in the Hanford Site represent the most intensive survey of its kind of any large geographic region in Washington and one of the few studies of its type conducted in the Pacific Northwest.

Almost 40,000 specimens have been collected and identified or made available for identification through these efforts by TNC. Thus far, 1,509 species-level identifications have been completed, and at least 500 more are expected. The actual number of insect species may reach as high as 15,500. Through the insect biodiversity inventory, a total of 41 species and 2 subspecies new to science have been identified and designated by world-recognized authorities. Additionally, numerous other specimens that have been collected but not yet identified may represent species new to science. The TNC surveys have resulted in the identification of 43 new taxa and 142 new findings in the state of Washington.

Butterflies, grasshoppers and darkling beetles are among the most conspicuous of insect species identified from specimens collected. Of particular interest are the butterflies and moths. Butterflies and moths (Lepidoptera) are one of the few groups of insects that are commonly included in biodiversity studies. Although other groups of insects offer as much potentially valuable information, butterflies and moths are indeed noteworthy for their use in estimating diversity. This is primarily because of their association with host plants. With few exceptions, butterflies and moths are plant feeders, and many are monophagous (i.e., one host plant used as food) or restricted to a limited number of related host plants. Thus, a diverse lepidopteran fauna often corresponds to a diverse flora. On the Hanford Site, 49 taxa of butterflies have been identified; 8 of these taxa are identified as monitor species by the state of Washington. To date, a total of 318 species of moths have been collected; 20 of these species are new to science, and 14 species represent new state records for Washington.

Shrub-steppe habitat has a relatively distinctive arthropod fauna, which appears to vary with the amount of disturbance and degradation within the habitat. Based on invertebrate collections thus far, it appears that shrub-steppe habitats in the Wahluke and Saddle Mountain Units are more degraded than that of the ALE. Several arthropod species that were encountered in habitats south and west of the Columbia River (e.g., snow scorpionflies [Mecoptera: Boreidae] and a winter scarab [Aphodius] new species [Coleoptera: Scarabaeidae]) were not found north of the river. The species richness of ground-dwelling beetles is also less in the Wahluke and Saddle Mountain Units. It should be noted that invertebrate collections on the ALE were made prior to the 2000 wildfire that severely altered some shrub-steppe habitats. Fire has been associated with reductions in total invertebrate family richness as well as in total taxa richness of predatory, detritus-feeding, and ground-dwelling invertebrates in shrub-steppe environments at Hanford.

Despite extensive and fruitful entomological diversity studies, very little is known concerning the arthropod fauna of the Monument. Species new to Washington State and new to science continue to be found. Such discoveries are likely to continue and accelerate if longer-term studies can be conducted, especially if surveys are focused on less-studied taxa. Large numbers of specimens in some of the lesser-known groups (e.g., spiders) have been collected and processed, and it is hoped that the identification and evaluation of these organisms will add significantly to an understanding of the biological diversity of the Monument. For these reasons, it is important to maintain representative native plant communities and generalized habitats, such as the few springs and riparian zones present in the Monument.

Entomological studies of the site indicate that the Hanford Site is unusual in its lack of introduced or pest species and in its abundance of native taxa. For example, wild bees are the most commonly encountered Hymenopterans in the Monument, an indication of the predominance of native vegetation on the site. In the surrounding urban and agricultural landscape, the introduced domesticated honeybee is most common. Agricultural pest species, such as corn earworm, alfalfa looper, celery looper, and numerous cutworms, make up the bulk of trap samples outside of the Hanford Site; these taxa are collected only in small numbers in the Hanford Site. The native arthropod fauna of the Hanford Site provides one of the few remaining areas where potentially beneficial native insects may be sought and, perhaps, found.

The key point about insect diversity in the Monument, however, is not that any single species is found here and no place else; rather, it is that so many species, including rare or rarely collected species, are found here. These findings indicate that the Monument still retains an assemblage of microhabitats large enough to support what at one time was a fauna typical of the arid interior West. The high diversity of insect species reflects the size, complexity and relatively undisturbed quality of the shrub-steppe habitat.

Facts About Invertebrates

1,509 species identified—so far!

41 new species.

2 new subspecies.

142 new findings in Washington.

318 moth species collected.

20 moth species new to science.

14 moth species new to Washington.

Green darner dragonflies eat 1 mosquito every 3 minutes and fly 35 mph.

Green darner dragonflies are Washington's official state insect.

Darkling beetles generate numerous calls to the FWS each spring when they emerge.

Page Photo Credits — Spiders - Jane Abel
Last Updated: May 20, 2013
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