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An endangered species is "a species at risk of extinction because of human activity, changes in climate, changes in predator-prey ratios, etc., especially when officially designated as such by a governmental agency such as the
U.S. Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...
". A spider is a member of the order Araneae, one of many orders within the class
arachnid Arachnida () is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaro ...
a, meaning it has a body consisting of two segments, a
cephalothorax The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...
and an
abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...
, as well as eight legs. All spiders are predators that feed off
insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of ...
, and some larger species have been known to catch small reptiles,
birds Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...
, and
amphibians Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...
(Levi and Levi, 2002). Until recently, insects and arachnids have not been considered for inclusion on threatened and endangered species lists. It was not until 1994 that most invertebrates were recognized as being as vulnerable as other fauna. Because of this, there are very few
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
of spiders listed as threatened or endangered and many are simply classified as "undetermined".


Endangered species

While many organizations agree completely on which spiders are endangered or threatened, a few commonly listed species are listed below.


Spruce-fir moss spider ('' Microhexura montivaga'')

The spruce-fir moss spider is listed as endangered under the U.S. Endangered Species Act of 1973. This spider resembles a tiny tarantula with adults measuring in at only 14.3 to 3.8 millimeters. It inhabits high-elevation forests in western North Carolina and eastern Tennessee. The species is extremely vulnerable to
desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
, causing it to shelter in damp shady areas such as shaded moss. The spider builds a tube shaped web between the moss and a rock or fir tree, hence the name.


Kauaʻi cave wolf spider ('' Adelocosa anops'')

The Kauaʻi cave wolf spider is found only on the island of Kauai in the U.S. state of Hawaii. As of 2006, this species can be found in a single cave and only 16 to 28 individuals have been encountered. Compared to other spider species, the Kauaʻi cave wolf spider has a low reproductive rate and due to habitat constraints, has little access to food sources. This spider is one of the largest documented cave-dwelling organisms measuring up to 8 centimeters. Because it spends its life in the darkness of a cave, this spider has no need for sight and is therefore completely eyeless.


Katipō (''

Latrodectus katipo ''Latrodectus'' is a broadly distributed genus of spiders with several species that are commonly known as the true widows. This group is composed of those often loosely called black widow spiders, brown widow spiders, and similar spiders. Howe ...
'')

The katipō spider is related to the Australian redback and other widow spiders. This spider can be found in New Zealand in burrows or trees. The name means "night-stinger" in native Maori. This species is listed as endangered due to habitat loss, as well as non-native spider introduction. It is estimated that only a few thousand of these spiders remain in the wild.


Vulnerable species

A vulnerable species is one listed by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...
as likely to become endangered unless the circumstances threatening its survival and reproduction improve.


Dolloff cave spider ('' Meta dolloff'')

While not listed as endangered, this spider is considered to be vulnerable to extinction. Much larger than ''Microhexura montivaga'', this spider ranges in size from 10 to 15 millimeters. This species makes large orb shaped webs at the entrance of
caves A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
and as of 2001 has only been found in caves located in
Santa Cruz, California Santa Cruz ( Spanish for "Holy Cross") is the county seat and largest city of Santa Cruz County, in Northern California. As of the 2020 census, the city population was 62,956. Situated on the northern edge of Monterey Bay, Santa Cruz is a pop ...
.


Great raft spider (''

Dolomedes plantarius The great raft spider or fen raft spider (''Dolomedes plantarius'') is a European species of spider in the family Pisauridae. Like other ''Dolomedes'' spiders, it is semiaquatic, hunting its prey on the surface of water. It occurs mainly in neutr ...
'')

The great raft spider is a declining species and is listed as vulnerable. It occurs throughout Europe but a lack of records make assessment of the species difficult. In the UK there are only three known populations, one stable, one threatened and one not assessed. This spider is a semi-aquatic species and its dependence on water may have led to the population's decline. The information on the great raft spider is very recent and due to a lack of historical records, the level of decline cannot be accurately measured.Smith, 2000


See also

* Endangered arthropods * List of U.S. federally endangered arthropods *
List of extinct arachnids This article contains a list of extinct species from the class Arachnida, with the year and location that they were last recorded. Extinct Extinct in the wild There are currently no known arachnids that are extinct in the wild yet still kept in ...


Notes


References

* Krajick, K. 2001. "Cave Biologists Unearth Buried Treasure". ''Science''. Vol. 293. pp. 2378–2381. * Levi, Herbert W. and Lorna R. Levi. 2002. ''Spiders and Their Kin''. St. Martin's Press. New York, U.S. * Smith, Helen. 2000. "The status and conservation of the fen raft spider (''Dolomedes plantarius'') at Redgrave and Lopham Fen National Nature Reserve, England". ''Biological Conservation''. Vol. 95. Issue 2. pp. 153–164. * Ubick, Darrell. 2001. ''Cavernicolous Invertebrates of Cave Gulch, Santa Cruz County, California''. Department of Entomology, California Academy of Sciences. San Francisco. * U.S. Fish and Wildlife Service. 2006. ''Recovery Plan for the Kauai Cave Arthropods: the Kauai Cave Wolf Spider (''Adelocosa anops'') and the Kauai Cave Amphipod (''Spelaeorchestia koloana'')''. U.S. Fish and Wildlife Service. Portland, Oregon. 64 pp. * U.S. Fish and Wildlife Service. 1995. ''Endangered and Threatened Wildlife and Plants; Spruce-Fir Moss Spider Determined To Be Endangered''. Federal Register. Vol.60. No. 24. pp. 6968–6974 {{threatened species, state=collapsed Spiders Endangered animals