What is a spruce-fir moss spider?
The spruce-fir moss spider lives in high-elevation forests of Fraser fir and red spruce. It’s found on moss mats growing on well-shaded rocks, which must be the perfect level of damp — not too dry and not too wet. It creates tube-shaped webs that connect to the moss and rock surfaces.
What is the habitat of a spruce tree spider?
The typical habitat of the spruce-fir moss spider is found in damp but well-drained moss and liverwort mats growing on thoroughly shaded rocks or boulders in mature, high-elevation Fraser fir ( Abies fraseri ) and red spruce ( Picea rubens ) forests.
What is the habitat of a moss spider?
First identified in 1923, it inhabits moss that grows on rocks underneath the forest canopy . M. montivaga is one of the smallest mygalomorph spiders, with adults only measuring 3 to 4 mm (about 1/8 inch).
What kind of spiders live in the Blue Ridge Mountains?
The high-elevation forests of the Blue Ridge provide habitat for a number of species not found at lower elevations, or anywhere else in the world. Among these unique species is the spruce-fir moss spider. At full size, the spruce-fir moss spider ( Microhexura montivaga) measures about 1/8”, making it the world’s smallest tarantula-like spider.
Where do moss spiders live?
Habitat. The spruce-fir moss spider lives in high-elevation forests of Fraser fir and red spruce. It's found on moss mats growing on well-shaded rocks, which must be the perfect level of damp — not too dry and not too wet. It creates tube-shaped webs that connect to the moss and rock surfaces.
Why is the spruce-fir moss spider endangered?
The denuded trunks of Fraser firs in Tennessee signal the deadly march of the balsam woolly adelgid, an invasive insect that has killed most Fraser firs in the Southern Appalachians. With the canopy gone, more heat and light dry out the mossy habitat of spruce-fir moss spiders.
What do spruce-fir moss spider eat?
The tiny spruce-fir moss spider constructs thin-walled tube-shaped webs between moss mats and rock surfaces. No food source has been discovered within these webs, suggesting that the SFMS likely feeds on springtails (collembolans) in the moss.
Is the spruce-fir moss spider a tarantula?
- About the size of a BB pellet, the spruce-fir moss spider is the world's smallest classified tarantula. - Found only on peaks above 5,300 feet, this arachnid was discovered on Mt. Mitchell in 1923, and because of its remote location and diminutive size, very little is known about it.
How many locations does the spruce fir moss spider live in?
In summary, the spruce-fir moss spider has been greatly reduced in number throughout its historic range; survives in only four locations, two of which have only one individual each; and has only one occurrence that might be described as currently stable, although this population is also threatened by many of the same factors that are believed to have resulted in the extirpation or decline of the other historically known populations. The four remaining populations are geographically isolated from one another, and three of them are so small as to have very little genetic variability left. All these circumstances make the spruce fir-moss spider endangered.
What is the threat to the spruce fir moss spider?
The primary threat to the survival of the spruce-fir moss spider is the rapid deterioration of its damp, high-elevation forest habitat. This habitat alteration and loss has been primarily brought about by the infestation of an exotic insect, air pollution precipitated out as acid rain, and past land use history. The spider is also threatened by factors that have not yet been fully identified, as well as by its very small population base that increases its vulnerability to stochastic extinction.
What is the spider in a spruce fir?
The spruce-fir moss spider, very sensitive to lack of moisture, requires situations of high and constant humidity , a microclimate which is regulated and preserved by the forest canopy. The dominant canopy species in the forest stands where the spider lives is the Fraser fir, and the decline and death of Fraser firs begins a cycle inimical to this species. As the canopy dwindles more unfiltered light reaches the forest floor, promoting evaporation in previously shaded damp areas and the eventual desiccation of the moss mats often found there without which this spider cannot survive. Dr. Frederick Coyle, a leading expert on the spruce-fir moss spider, provides some anecdotal commentary on this problem in a 1991 letter sent to Keith Langdon. Dr. Coyle writes that the spider, common at one of the Swain County sites as late as 1983, had become extremely rare only five years later. He states that many of the moss mats at this site had become dry and loose, due largely, in his opinion, to deterioration of the forest canopy at the site.
How many eggs do spiders lay?
The egg sac, thin-walled and nearly transparent, may contain seven to nine eggs, laid in June. The female remains with the egg sac and, if disturbed, will carry the egg sac with her fangs. Spiderlings emerge in September. The means of dispersal of the spiderlings from the parental moss mat is not known. Ballooning, a process by which the spiders use a sheet of silk played out into the wind to carry them into the air, has been suggested as a possible means of long-range dispersal, but this species's high sensitivity to desiccation would likely preclude this dispersal method. The life span of the species is also unknown, although experts in the field have estimated that it may take three years for the species to reach maturity.
Where are moss spiders found in North Carolina?
Status surveys conducted from 1989 through 1992 for the spruce-fir moss spider at its five historic locations and in other seemingly suitable habitat found the spider at only three sites in western North Carolina and one in eastern Tennessee. The historic North Carolina occurrence in Yancy County appears to have been extirpated, and only the population located along the Avery County and Caldwell County line in North Carolina seems relatively stable. The two other North Carolina populations are located in Swain County.
Is a spruce fir moss spider valuable?
The spruce-fir moss spider is not currently known to be commercially valuable; however, because of its extreme rarity and uniqueness, it is conceivable that it could be sought by collectors. This spider is one of only two members of the genus Microhexura, is the only representative of the primitive family Dipluridae in eastern North America, and is one of the smallest of the world's "tarantulas." While collecting or other intentional take is not presently identified as a factor contributing to the decline of this species, the low numbers, slow reproductive rate, and extremely restricted range of the spruce-fir moss spider make it unlikely that the species could withstand even moderate collecting pressure.
Where do spruce fir moss spiders live?
The spruce-fir moss spider ( Microhexura montivaga) is an endangered species of spider found at high elevations in the southern Appalachian Mountains. First identified in 1923, it inhabits moss that grows on rocks underneath the forest canopy .
Where do moss spiders live?
The spruce-fir moss spider ( Microhexura montivaga) is an endangered species of spider found at high elevations in the southern Appalachian Mountains. First identified in 1923, it inhabits moss that grows on rocks underneath the forest canopy .
What is the smallest spider?
M. montivaga is one of the smallest mygalomorph spiders, with adults only measuring 3 to 4 mm (about 1/8 inch). The coloration varies from light brown to yellow-brown to a darker reddish brown, with no markings on the abdomen.
Why are Fraser firs endangered?
montivaga, and the spider species was listed as endangered in 1995. Many Fraser firs have died due to infestation with Adelges piceae, the balsam woolly adelgid, an insect pest introduced from Europe.
Is the Tennessee spider population extirpated?
The Tennessee population, located in Sevier County, was considered healthy up to 1989, but is now possibly extirpated. On two locations in North Carolina, there was only one spider found each in recent years. Only the population along the Avery/Caldwell County line in North Carolina seems to be relatively stable. This population appears to be restricted to the moss mats on a single rock outcrop and a few surrounding boulders.
What do spruce fir spiders eat?
No food source has been discovered within these webs, suggesting that the SFMS likely feeds on springtails ( collembolans) in the moss. In June, the SFMS female lays 7-9 eggs in a thin-walled, translucent egg sac. She remains with the egg sac until her spiderlings hatch out in September.
What is the smallest spider in the world?
At full size, the spruce-fir moss spider ( Microhe xura montivaga) measures about 1/8”, making it the world’s smallest tarantula-like spider. This rare arachnid only occurs in the high-elevation red spruce-Fraser fir forests of the Southern Appalachian Mountains, with six recognized populations occurring on the mountain peaks of Virginia, Tennessee, and North Carolina above 5,300 feet. In its peak condition, the spruce-fir ecosystem has a dense canopy and moist understory. The spruce-fir moss spider (SFMS) takes advantage of this quality by living below damp, well-drained moss and liverwort mats on heavily shaded north-facing rock outcroppings.
Description
- The spruce-fir moss spider, Microhexura montivaga, was originally described in 1925 from collections made two years earlier in the mountains of western North Carolina. Only a few specimens were taken, and little was known about the species until its rediscovery approximately 50 years later. M. montivaga is one of only two species belonging to the genus Microhexura, the …
Behavior
- There is no record of prey having been found in the webs of the spruce-fir moss spider, and so its food sources are unknown. The egg sac, thin-walled and nearly transparent, may contain seven to nine eggs, laid in June. The female remains with the egg sac and, if disturbed, will carry the egg sac with her fangs. Spiderlings emerge in September. The means of dispersal of the spiderlings …
Habitat
- The typical habitat of the spruce-fir moss spider is found in damp but well-drained moss and liverwort mats growing on thoroughly shaded rocks or boulders in mature, high-elevation Fraser fir (Abies fraseri ) and red spruce (Picea rubens) forests. The forest stands at the sites where the species has been observed are composed primarily of Fraser fi...
Distribution
- Status surveys conducted from 1989 through 1992 for the spruce-fir moss spider at its five historic locations and in other seemingly suitable habitat found the spider at only three sites in western North Carolina and one in eastern Tennessee. The historic North Carolina occurrence in Yancy County appears to have been extirpated, and only the population located along the Avery …
Threats
- The primary threat to the survival of the spruce-fir moss spider is the rapid deterioration of its damp, high-elevation forest habitat. This habitat alteration and loss has been primarily brought about by the infestation of an exotic insect, air pollution precipitated out as acid rain, and past land usehistory. The spider is also threatened by factors that have not yet been fully identified, a…
Conservation and Recovery
- The U.S. Fish and Wildlife Service (FWS) believes that a detailed characterization of the spruce-fir moss spider's habitat, better knowledge of threats to this habitat, and additional information concerning its biology will be necessary in order to properly manage and implement protection and recovery measures. These, as well as other research needs and activities necessary to ensu…
Contacts
- U.S. Fish and Wildlife Service Regional Office, Division of Endangered Species 1875 Century Blvd., Suite 200 Atlanta, Georgia 30345 http://southeast.fws.gov/ U.S. Fish and Wildlife Service Asheville Field Office 330 Ridgefield Court Asheville, North Carolina 28806 (704) 665-1195 ext. 225
References
- Coyle, F. A. 1985. Observations on the Mating Behavior of the Tiny Mygalomorph Spider, Micro-hexura montivaga Crosby & Bishop (Araneae, Dipluridae). Bulletin. British Arachnological Society6 (8): 328-330. Eagar, 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 Spruc…
Overview
The spruce-fir moss spider (Microhexura montivaga) is an endangered species of spider found at high elevations in the southern Appalachian Mountains. First identified in 1923, it inhabits moss that grows on rocks underneath the forest canopy.
Description
M. montivaga is one of the smallest mygalomorph spiders, with adults only measuring 3 to 4 mm (about 1/8 inch). The coloration varies from light brown to yellow-brown to a darker reddish brown, with no markings on the abdomen. The chelicerae project forward, and one pair of spinnerets is very long. It possesses a second pair of book lungs, which appear as light patches behind the genital furrow.
Biology
M. montivaga constructs tube-shaped webs, apparently for shelter, as prey has never been found in them. It probably feeds on springtails that are abundant in moss mats. M. montivaga can take as long as three years to reach maturity, due to low temperatures and resulting slow metabolism.
Endangered status
The widespread death of Fraser fir trees has destroyed many habitats for M. montivaga, and the spider species was listed as endangered in 1995. Many Fraser firs have died due to infestation with Adelges piceae, the balsam woolly adelgid, an insect pest introduced from Europe. The resulting thinning of the forest canopy leads to the drying of the moss mats that are essential for the spider's survival, as it requires climates of high and constant humidity. These spiders have s…
Distribution
M. multivaga is known from Fraser fir and red spruce forests on mountain peaks at and above 1,650 m (5,410 ft) in the Southern Appalachian Mountains of North Carolina and Tennessee. It has been recorded from Clingmans Dome and Mount Collins (both very small populations), Mount Le Conte, Mount Mitchell (probably extirpated), Grandfather Mountain, and Roan Mountain.
The Tennessee population, located in Sevier County, was considered healthy up to 1989, but is n…
External links
• "Spruce-fir moss spider", Asheville Ecological Services Field Office, U.S. Fish and Wildlife Service, retrieved 2016-03-15
Further reading
• Crosby CR, Bishop SC (1925). "Two New Spiders from the Blue Ridge Mountains of North Carolina (Araneina)". Entomological News 36: 142-146. ("Microhexura montivagus [sic]", new species, pp. 145–146).