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Home/Species/ Spruce-fir Moss Spider

Microhexura montivaga

Crosby and Bishop, 1925

Spruce-fir Moss Spider

G2Imperiled Found in 7 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.106879
Element CodeILARA33010
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryInvertebrate Animal
Endemicendemic to a single nation
KingdomAnimalia
PhylumArthropoda
ClassArachnida
OrderAraneae
FamilyDipluridae
GenusMicrohexura
Other Common Names
North Carolina Funnelweb Tarantula (EN) spruce-fir moss spider (EN)
Concept Reference
Platnick, N.I. 2002. The world spider catalog, Version 2.5. The American Museum of Natural History. Online. Available: http://research.amnh.org/entomology/spiders/catalog81-87/index.html
Conservation Status
Rank MethodLegacy Rank calculation - Excel v3.1x
Review Date2018-12-17
Change Date2018-12-17
Edition Date2018-12-17
Edition AuthorsAlmquist, D. T. (2018), Capuano, N. (2005)
Threat ImpactHigh
Range Extent5000-20,000 square km (about 2000-8000 square miles)
Number of Occurrences6 - 20
Rank Reasons
There are at least 20 total occurrences, although only about half have been documented within the past 20 years and there is some evidence of decline, mostly due to decline of the Fraser Fir, Abies fraseri by the infestation of the balsam wooly adelgid.
Range Extent Comments
Occurs in the southern Appalachian Mountains. Total historical range based on NatureServe records is approximately 7,500 square kilometers, with range based upon occurrences documented within the past 20 years being somewhat less at approximately 6,500 square kilometers.
Occurrences Comments
There are NatureServe records for 22 occurrences, with 11 of these having been documented within the past 20 years.
Threat Impact Comments
The primary threat is loss of suitable moss habitat due to the decline of the Fraser Fir, Abies fraseri by the infestation of the balsam wooly adelgid, Adelges picea (Homoptera, Adelgidae), a nonnative insect pest (USFWS 1998).

Other potential threats are complex and controversial and include regional-scale air pollution (acid rain), past land use history (past logging and burning practices in the Southern Appalachians), vulnerability to extirpation from a single event or activity (i.e. drought, wildfire or timber harvesting) and human trampling/disturbance of the moss mats and surrounding vegetation shading the moss mats (USFWS 1998).
Ecology & Habitat

Description

A small mygalomorph spider (2.5 - 3.8 mm adult size) ranging in color from light brown to a darker reddish brown. There are no markings on the abdomen and the carapace is generally yellowish brown (Harp 1992).

Diagnostic Characteristics

The very long spinnerets are the easiest family level character and Levi et al. (1968) illustrate two of the ten or so North American species. Reliable field identification characteristics include chelicerae that project forward well beyond the anterior edge of the carapace, a pair of very long posterior spinnerets, and the presence of a second pair of book lungs, which appear as light patches posterior to the genital furrow (Harp 1992) (USFWS 1995).

Habitat

Lives in high-elevation spruce-fir forest communities on moist but well-drained moss mats growing on rocks and boulders in well-shaded locations. It is known from conifer forests dominated by red spruce, Picea rubens, and Fraser Fir, Abies fraseri (USFWS 1995).
Terrestrial Habitats
Forest - Conifer
Other Nations (1)
United StatesN1
ProvinceRankNative
North CarolinaS1Yes
TennesseeS1Yes
VirginiaS1Yes
Threat Assessments
ThreatScopeSeverityTiming
5 - Biological resource useUnknownUnknownUnknown
5.3 - Logging & wood harvestingUnknownUnknownUnknown
7 - Natural system modificationsUnknownUnknownUnknown
7.1 - Fire & fire suppressionUnknownUnknownUnknown
8 - Invasive & other problematic species, genes & diseasesPervasive (71-100%)Serious or 31-70% pop. declineHigh (continuing)
8.1 - Invasive non-native/alien species/diseasesPervasive (71-100%)Serious or 31-70% pop. declineHigh (continuing)
9 - Pollution———
9.5 - Air-borne pollutantsPervasive (71-100%)UnknownUnknown
9.5.1 - Acid rainPervasive (71-100%)UnknownUnknown

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Roadless Areas (7)
North Carolina (7)
AreaForestAcres
Balsam ConePisgah National Forest10,591
BearwallowPisgah National Forest4,113
Craggy MountainPisgah National Forest2,657
Graveyard Ridge (addition)Pisgah National Forest1,958
Laurel MountainPisgah National Forest5,683
Middle Prong AdditionPisgah National Forest1,852
Sam Knob (addition)Pisgah National Forest2,576
References (8)
  1. Coyle, F. A. 1981. The mygalomorph spider genus <i>Microhexura</i> (Araneae, Dipluridae). Bulletin of the American Museum of Natural History. 170:64-75.
  2. Coyle, F. A. 1985. Observations on the mating behaviour of the tiny mygalomorph spider, Microhexura montivaga Crosby &amp; Bishop (Araneae, Dipluridae). Bulletin of the British Arachnological Society 6(8):328-330.
  3. Eager, C. 1984. Review of the biology and ecology of the balsam woolly aphid in southern Appalachian spruce-fir forests. In: P.S. White, ed. The southern Appalachian spruce-fir ecosystem: its biology and threats. U.S. Department of the Interior, National Park Service, Research/Resources Management Report SER-71. 268 pp.
  4. Harp, J. M. 1992. A Status Survey for the Spruce-Fir Moss Spider, <i>Microhexura Montivaga</i> Crosby and Bishop (Araneae, Dipluridae), North Carolina Wildlife Commission, Nongame and Endangered Wildlife Program, and the U.S. Fish and Wildlife Service, Asheville, North Carolina. 30 pp.
  5. Levi, H. W., L. Levi, and H. S. Zim. 1968. A guide to spiders and their kin. Golden Nature Guides, Golden Press, New York City, NY. 160pp.
  6. Platnick, N.I. 2002. The world spider catalog, Version 2.5. The American Museum of Natural History. Online. Available: http://research.amnh.org/entomology/spiders/catalog81-87/index.html
  7. U.S. Fish and Wildlife Service (USFWS). 1995. Endangered and Threatened Wildlife and Plants: Spruce-Fir Moss Spider Determined to be Endangered. Final Rule. Federal Register. 60(24):6968-74.
  8. U.S. Fish and Wildlife Service (USFWS). 1998. Recovery plan for the Spruce-fir Moss Spider. Atlanta, GA. 22 pp.