Coffin Cave Mold Beetle

Batrisodes texanus

Description

The Coffin Cave mold beetle is a small, long-legged eyeless beetle with short elytra leaving five abdominal tergites which are exposed. It has no metathoracic wings. The body length of this species is measured at 0.10-0.11 in (2.6-2.88 mm). The males possess a vague groove across the head anterior to the antennal bases. The lateral sides of the head are smooth, curved and flat. A few granules are observed where one might think the eyes should be.

Behavior

Sexual dimorphism is observed in that the female lacks the transverse impression anterior to the antennal bases. The tenth antennal segment is somewhat wider and longer than the ninth. In males the tenth antennal segment is twice as wide as the ninth.

The Coffin Cave mold beetle is a troglobite. A troglobite is a species which spends its entire life in openings underground usually with small or absent eyes, attenuated appendages, and other adaptations to its subsurface dwelling.

Habitat

This species spends its entire life underground. It is endemic to the karst (limestone) formations. These formations include caves, sinkholes, and other subterranean voids. It is dependent on outside moisture and nutrient inputs generated from the subsurface. This species inhabits areas of the cave where temperature and humidity are constant.

The surface vegetation ranges from pasture land to mature oak-juniper woodland.

Karst is formed by the slow dissolution of calcium carbonate from limestone bedrock by mildly acidic ground water. This process results in subterranean voids resembling a honeycomb. The water enters the subsurface through cracks, crevices, and other openings, dissolving soluble beds of rock.

Nutrients to this ecosystem are provided from the outside surface washed in. These nutritional sources include plant material, feces, eggs, and carrion. Cave crickets are believed to provide an important component to the nutritional balance of this cave ecosystem. These crickets introduce nutrients through eggs, feces, nymphs, and dead body parts on which many invertebrates are known to feed.

Distribution

As this species was not described until 1992, its past distribution is not known. This species occurs in two caves in the North Williamson County karst fauna region and three caves in the Georgetown karst fauna region in Williamson County, Texas.

Threats

The primary threat to the Coffin Cave mold beetle is habitat loss due to urban development activities. Continued urban expansion such as residential subdivisions, schools, golf courses, roads, commercial and industrial facilities, etc. poses a threat in the form of cave filling or collapse, water diversion, vegetation/fauna alteration, and increased pollution.

Some caves have already been filled as a result of road construction and building site preparation. Development directly above caves could result in the collapse of cave ceilings.

Ranchers may have also filled some caves. Justification is placed in reducing hiding places for predators of cattle and goats as well as preventing these animals from falling into the formations.

Troglobites rely upon and in fact require a controlled environment of high humidity and constant temperature. If water drainage paths are altered, this balance is no longer on an even keel. Water diversion away from the caves could lead to the direct mortality of this species. Increased water infiltration could lead to flooding and loss of air space.

As the karst ecosystem relies on the infiltration of nutrients from the surface, a fluctuation in the vegetation or fauna would alter nutrient supplies. During development, native vegetation may be replaced with non-native species, as well as cause the introduction of exotic animal species, such as fire ants. An overall nutrient depletion would result. The removal of vegetation could also lead to temperature fluctuations, a change in moisture regime and potential for contamination and increased sedimentation from soil erosion.

Conservation and Recovery

A Recovery Plan was published for the Coffin Cave mold beetle in 1994. The conservation of this rare insect requires the strict protection of its cave habitat from disturbances and other changes associated with residential, agricultural, or commercial development. Other necessary actions include studies to monitor the abundance of the Coffin Cave mold beetle and research into its biology and habitat needs. There should also be a public education campaign to develop a broad base of support for the protection of rare cave habitats.

Contact

U.S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 1306
Albuquerque, New Mexico 87103
Telephone: (505) 766-2321
Fax: (505) 766-8063
www://southwest.fws.gov/

References

U.S. Fish and Wildlife Service. 1993. "Endangered and Threatened Wildlife and Plants; Coffin Cave Mold Beetle (Batrisodes texanus ) and the Bone Cave Harvestman (Texella reyesi ) Determined to Be Endangered." Federal Register 58(158): 43818-43819.

U.S. Fish and Wildlife Service. 1994. Recovery Plan for Endangered Karst Invertebrates in Travis and Williamson Counties, Texas. Albuquerque, New Mexico.