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Tiny brown spider with a white egg sac on a moist forest surface
Information icon U.S. Fish and Wildlife Service biologist Susan Cameron visited Mount Craig in July, 2019 to search for the spider. Her effort was met with success as she logged the first known occurrence of the spider on the mountain. Photo by Gary Peeples, USFWS.

Spruce-fir moss spider

Microhexura montivaga


The spruce-fir moss spider is one of the smallest members of the primitive suborder of spiders, Mygalomorphae, which includes tarantulas and trapdoor spiders. Adults measure only 0.10 to 0.15 inch (about the size of a BB). Colors of the spruce-fir moss spider ranges from light brown to yellow-brown to a darker reddish brown, and there are no markings on its abdomen.


The spruce-fir moss spider only lives on the highest mountain peaks in the Southern Appalachian Mountains of western North Carolina, eastern Tennessee, and southwest Virginia. The spider is largely found in fir and spruce-fir forests over 5400 feet in elevation and on slopes with northern aspects. The typical habitat of this spider is damp, but well-drained moss mats growing on rocks and boulders in well-shaded areas within these forests. The moss mats cannot be too dry (the species is very sensitive to desiccation).




The spruce-fir moss spider is limited to a handful of mountains in western North Carolina, eastern Tennessee, and southwest Virginia

Conservation challenges

The surviving populations of the spruce-fir moss spider are restricted to small areas of suitable moss mats on a few scattered rock outcrops and boulders beneath fir and spruce trees in fir and spruce-fir forests. Destruction of the moss mats (or even a portion of the mats) or damage to the surrounding vegetation shading the mats could result in the loss of entire populations or even extinction of this species.

Fraser fir trees throughout the Southern Appalachian Mountains have suffered extensive mortality due to infestation by the balsam wooly adelgid, an invasive insect pest believed to have been introduced into the United States from Europe. Most mature Fraser firs are easily killed by the adelgid, with death occurring in two to seven years from infestation. The remaining trees become more susceptible to exposure, wind, and storm damage. The red spruce trees are not damaged by the insect.

During the past century, most of the Southern Appalachian spruce-fir forest has suffered extensive changes and declines in size and/or vigor because of past logging and burning practices, storm damage, air pollution, climate change, disease, insect damage, and exposure shock.

As the spruce-fir forest decreases in health and size, the death and thinning of the tree canopy results in locally drastic changes in the microclimate, including increased temperatures and decreased moisture. This leads to the drying of the moss mats on which the spider depends for its survival. The spruce-fir moss spider is very sensitive to desiccation and requires climates of high and constant humidity. As the mats dry out, so does the spider.

Recovery plan

Download the recovery plan for the spruce-fir moss spider (Microhexura montivaga).

Partnerships, research and projects

The Southern Appalachian Spruce Restoration Initiative is an effort that includes the U.S. Forest Service, The Nature Conservancy, Southern Highlands Reserve, the U.S. Fish and Wildlife Service, the North Carolina Wildlife Resources Commission, and other partners to restore red spruce to areas where it was lost due to logging and subsequent fires around the turn of the 20th century. The effort should result in expanded habitat for the spruce-fir moss spider.

How you can help

Tread lightly and stay on designated trails. Vegetation on popular high mountains has virtually been destroyed by human trampling.

Look for opportunities to help steward high-elevation forests or support efforts to restore these forests. Possibilities include the Pisgah and Nantahala National Forests, Great Smoky Mountains National Park, the Blue Ridge Parkway, Southern Highlands Reserve, N.C. Wildlife Resources Commission, Mount Mitchell and Grandfather Mountains state parks in North Carolina, Virginia’s Grayson Highlands State Park, and the Southern Appalachian Highlands Conservancy.

Visit high-elevation sites in the Southern Appalachians to learn about and experience these sites first hand. Easily accessible sites are available at Mount Mitchell State Park, Grayson Highlands State Park, Grandfather Mountain State Park, Roan Mountain on the Pisgah National Forest, and Clingman’s Dome in Great Smoky Mountains National Park.

Subject matter experts

Designated critical habitat

Designated, July 6, 2001. 66 FR 35547 35566

Federal Register notices

The following Federal Register documents were automatically gathered by searching the Federal Register Official API with this species’ scientific name ordered by relevance. You can conduct your own search on the Federal Register website.

  • We're sorry but an error occurred. Visit the Federal Register to conduct your own search.

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