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Insects and Spiders - Threatened And Endangered Arachnid Species In The United States

cave fws listed expenditures

As of March 2006 there were twelve U.S. species of arachnids listed under the ESA, as shown in Table 10.3. All of the arachnids have endangered status, and six of them have recovery plans in place. The imperiled arachnids fall into four species types, as follows:

  • Harvestmen—three species
  • Meshweaver—four species
  • Pseudoscorpion—one species
  • Spider—four species

Ten of the arachnids are cave-dwelling species found only in Texas. The only imperiled arachnids outside of Texas are the Kauai cave wolf spider, which inhabits Hawaii, and the spruce-fir moss spider, which is found in North Carolina and Tennessee.

Table 10.3 also lists the expenditures made under the Endangered Species Act for arachnid species during fiscal year 2004. In total, $1.55 million was spent. The Bone Cave harvestman, a Texas species, accounted for $1.36 million of this total.

Texas Cave Arachnids

Ten of the listed arachnids are found only in underground karst caves in a handful of counties in Texas. (See Figure 10.4.) Karst is a geological term referring to a type of underground terrain resulting when limestone bedrock is exposed to mildly acidic groundwater over a long period of time. Eventually the bedrock becomes a honeycomb of cracks, fissures, holes, and other openings. There are dozens of these karst caves located in Bexar, Travis, and Williamson counties in Texas. In recent decades scientists have discovered unusual invertebrate species living in these caves. The tiny cave dwellers are eyeless and have no pigment (color) to their bodies. Ten of the creatures have been added to the endangered species list. They include two true spiders, one pseudo-scorpion, four meshweavers (tiny web-making arachnids), and three harvestmen (commonly known as "daddy longlegs" or "granddaddy longlegs").

The species were listed under the Endangered Species Act after a collection of conservation groups petitioned the U.S. Fish and Wildlife Service in 1992. The creatures were listed as endangered in 2000. In 2003 approximately 1,000 acres were designated as critical habitat for six of the arachnids. In addition, four of the species are included in a recovery plan published in 1994 TABLE 10.3 Endangered and threatened arachnid species in the United States, March 2006 and expenditures for them in fiscal year 2004 Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, March 6, 2006, http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort=1 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=I&listingType=L (accessed March 6, 2006), and adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)that also covers other imperiled invertebrate species living in the caves.

TABLE 10.3
Endangered and threatened arachnid species in the United States, March 2006 and expenditures for them in fiscal year 2004
Common name Scientific name Lisinga Recovery Plan date Recovery plan statusb Expenditures under ESA in fiscal year 2004
aE=endangered.
bRecovery plan stages: F=final and D=draft.
SOURCE: Adapted from "Listed FWS/Joint FWS and NMFS Species and Populations with Recovery Plans (Sorted by Listed Entity)" and "Listed U.S. Species by Taxonomic Group," in Threatened and Endangered Species System (TESS), U.S. Department of the Interior, U.S. Fish and Wildlife Service, March 6, 2006, http://ecos.fws.gov/tess_public/SpeciesRecovery.do?sort=1 and http://ecos.fws.gov/tess_public/SpeciesReport.do?kingdom=I&listingType=L (accessed March 6, 2006), and adapted from "Table 1. Reported FY 2004 Expenditures for Endangered and Threatened Species, Not Including Land Acquisition Costs," in Federal and State Endangered and Threatened Species Expenditures: Fiscal Year 2004, U.S. Department of the Interior, U.S. Fish and Wildlife Service, January 2005, http://www.fws.gov/endangered/expenditures/reports/FWS%20Endangered%20Species%202004%20Expenditures%20Report.pdf (accessed February 11, 2006)
Harvestman, Bee Creek Cave Texella reddelli E 8/25/94 F $7,140
Harvestman, Bone Cave Texella reyesi E 8/25/94 F $1,361,780
Harvestman, Cokendolpher Cave Texella cokendolpheri E None $10,000
Meshweaver, Braken Bat Cave Cicurina venii E None $10,160
Meshweaver, Government Canyon Bat Cave Cicurina vespera E None $10,160
Meshweaver, Madla's Cave Cicurina madla E None 60,160
Meshweaver, Robber Baron Cave Cicurina baronia E None $10,160
Pseudoscorpion, Tooth Cave Tartarocreagris texana E 8/25/94 F $8,660
Spider, Government Canyon Bat Cave Neoleptoneta microps E None $10,160
Spider, Kauai cave wolf or pe'e pe'e maka 'ole Adelocosa anops E 2/9/05 D $32,101
Spider, spruce-fir moss Microhexura montivaga E 9/11/98 F $13,500
Spider, Tooth Cave Leptoneta myopica E 8/25/94 F $11,320

Kauai Cave Wolf Spider

The Kauai cave wolf spider, ranging from about one-half to three-quarters of an inch in length, is a blind species found only in special caves on the southern part of the island of Kauai in Hawaii. These caves are formed by young lava flows. Unlike most other spiders, which trap their prey in webs, the Kauai cave wolf spider hunts its prey directly. Its prey includes the Kauai cave amphipod, a species that is also highly endangered. The FWS originally listed both species as endangered in January 2000. Female cave wolf spiders lay some fifteen to thirty eggs per clutch, and carry young on their backs after hatching. Cave species are extremely sensitive to changes in temperature and light. In 2005 the Fish and Wildlife Service published a draft recovery plan covering both imperiled invertebrates living in the Kauai cave. The critical habitat established for the species includes fourteen units totaling 272 acres on the southern part of the island.

Spruce-fir Moss Spider

The spruce-fir moss spider is an endangered spider related to the tarantula. It was placed on the Endangered Species List in 1995. Spruce-fir moss spiders live in moss mats found only in the vicinity of Fraser fir trees. Its populations have declined largely due to the introduction in the United States of an invasive European insect species, the balsam-woolly adelgid. The balsam-woolly adelgid infests Fraser fir trees, causing them to die within a time period of two to seven years. With the death of numerous fir trees, other forest trees have also blown over. The resulting increase in light level and temperature causes the moss mats on the forest floor to dry up.

In 2001 the U.S. Fish and Wildlife Service designated critical habitat for the species, including areas in the Great Smoky Mountains National Park and the Pisgah and Cherokee National Forests, as well as a preserve managed by the Nature Conservancy. This designation of critical habitat followed a lawsuit against the agency, which had previously deemed designating critical habitat "not prudent" because it believed the spider would be more vulnerable to collectors.

FIGURE 10.4 A karst cave provides habitat for endangered invertebrates "Front Cover" in Endangered Karst Invertebrates (Travis and Williamson Counties, Texas) Recovery Plan, U.S. Department of the Interior, U.S. Fish and Wildlife Service, August 25, 1994, http://ecos.fws.gov/docs/recovery_plans/1994/940825.pdf (accessed March 2, 2006)

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