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Cyclocosmia torreya Gertsch and Platnick, 1975

Torreya Trap-door Spider

Federal Protection: No US federal protection

State Protection: No Georgia state protection

Global Rank: GNR

State Rank: SU

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 6

Habitat Summary for element in Georgia: Hardwood ravines


Description

This mygalomorph spider is large (25 mm [1.0 inch] in total length). Females are a shiny, chestnut brown in color. Males are dark-brown to black. The chelicerae/fangs are oriented parallel. Compact body form with an abruptly truncated abdomen that ends in a heavily sclerotized disc (resembles a manhole cover).

Similar Species

The unique shape of the abdomen and large body size distinguish this spider from all other mygalomorph spider species native to Georgia except the morphologically similar Cyclocosmia truncata. In C. torreya, the abdomen has 22 ribs on each side and the abdominal rib angles protrude from the seam of the abdominal disc; in C. truncata the abdomen has 24 ribs on each side and they do not protrude from the from the seam of the abdominal disc. C. truncata, confined to the Ridge and Valley and Piedmont provinces of north Georgia and adjacent states, is allopatric with the Coastal Plain C. torreya.

Habitat

This spider is restricted to mesic slope hardwood forest habitats (i.e., evergreen−broadleaf deciduous forests, often referred to as “oak-beech-magnolia” communities due to the prevalence of Quercus alba. (white oak), Fagus grandifolia (American beech), and Magnolia grandiflora (southern magnolia). Such environments are uncommon, highly localized, and limited to steep, usually north-facing slopes or bluffs. The north-facing bluffs and ravines associated with two drainages in particular − the Chattahoochee River and the Savannah River − are especially important habitat for this spider as well as noteworthy refugia for plant and animal species with northern, mountain-province affinities. These spiders prefer humid ravines where they inhabit steep slopes and near vertical moss-and-fern-lined banks of small streams.

Diet

These spiders, accomplished sit-and-wait predators, feed on a wide variety of other arthropod species.

Life History

These spiders construct burrows in sandy to clay soils covered with moist leaf litter. The burrows average about 10-15 cm [4-6 inches] deep and are capped with a thin, wafer-type (and extraordinarily well-camouflaged) trap door. When threatened, these spiders retreat head-first into their burrows until the truncated abdomen is in tight contact with the sides of the tunnel, thus, presenting to any potential predator a facade resembling a manhole cover (some pompilid wasps are major parasitoids of mygalomorph spiders). Females seldom, if ever, leave their burrows. Upon reaching sexual maturity, males abandon their burrows go on lengthy sojourns in search of females. Ravine trapdoor spiders are slow to mature and very long-lived (captives have lived over to 12 years). Due to their limited dispersal ability and pronounced longevity the species tends to occur in colonies. In Georgia, mygalomorph spider taxa that are known to co-occur with C. torreya include Sphodros rufipes, Myrmekiaphila torreya, and Antrodiaetus unicolor.

Survey Recommendations

Very difficult to find in the wild due to its narrow ecological requirements and the extremely effective camouflage of the trapdoor. Males are especially poorly represented in museum collections. Field methods to find these spiders include drift fences with pitfall traps, shining stream banks at night, and disclosing burrows by using a leaf blower or rake to uncover them. Given that Cyclocosmia torreya has been collected at a site located in the Suwannee River drainage of northern Florida (Ichetucknee Springs, Columbia County), surveys recommended for mesic slope forests associated with this drainage in south-central Georgia

Range

In Georgia, Cyclocosmia torreya is known from fewer than 10 locations (all Coastal Plain), including sites in the extreme southwestern part of the state (Chattahoochee Ravines and Torreya Ravines provinces) and sites associated with bluffs on the south side of the Savannah River, as far south as Effingham County. Previous to recent (2018) surveys, there was only a single published record for the state (Clay County).

Threats

Populations disappeared from a Florida ravine that was damaged by wild pigs (Sus scrofa) and lumbering. Wild pigs are present at most of the known sites for this spider in Georgia, and pig control/eradication should be undertaken. The steep slopes of C. torreya habitats generally make logging impractical, regardless, logging of spider sites is apt to result in damage to these habitats. An introduced plant, Ardisia crenata (Primulaceae; introduced through the horticultural trade from Asia), is now weedy and abundant on mesic slopes and in stream bottoms, including at several C. torreya sites in southwestern Georgia.

Georgia Conservation Status

Of the very few Georgia sites (< 10) known for this species, at least three are protected by virtue of being on public land. Some populations are threatened by the presence of wild pigs and invasive plants.

Conservation Management Recommendations

Additional Georgia surveys for this spider are warranted. Recent records for the Savannah River drainage are of considerable zoogeographic interest in that they are the first for this species and genus for the Atlantic Coastal Plain and may represent an undescribed species. Control of wild pigs and invasive plants (e.g., Ardisia crenata [Myrsinaceae]) should be conducted at sites known to support this spider.

References

Bond, J.E., and B.E. Hendrixson. 2017. Chapter 8: Ctenizidae. Pp. 51−52, In D. Ubick, P. Paquin, P.E. Cushing, and V. Roth (Eds.). Spiders of North America: an Identification Manual, Second Edition. American Arachnological Society, Keene, NH. 425 pp.

Bourguignon, K. 2018. Deep genetic divergence in the Deep South: an integrative approach to species delimitation reveals the paraphyletic nature of speciation in the trapdoor spider genus Cyclocosmia. Master’s Thesis, Auburn University, Auburn, Alabama.

Bradley, R.A. 2013. Common Spiders of North America. University of California Press. Berkeley, California. 271 pp.

Gertsch, W.J., and N.I. Platnick. 1975. A revision of the trapdoor spider genus Cyclocosmia (Araneae, Ctenizidae). American Museum Novitates 2580: 1−20.

Wallace, H.K., and G.B. Edwards. 1994a. Torreya trap-door spider, Cyclocosmia torreya Gertsch and Platnick. Pp. 242−244, In M. Deyrup and R. Franz (Eds.).

Rare and Endangered Biota of Florida, Volume 4: Invertebrates. University Press of Florida, Gainesville, Florida. 798 pp.

Authors of Account

Dirk J. Stevenson

Date Compiled or Updated

December 1st 2018

Photo By Daniel Dye. Image may be subject to copyright.